Murder of Crows
1B
Creature – Bird (Uncommon)
1/1
Flying
When Murder of Crows enters the battlefield, if its rebirth cost was paid, return all cards named Murder of Crows from your graveyard to the battlefield.
Rebirth 4B (You may cast this card from your graveyard for its rebirth cost. If you do, it enters the battlefield with a death counter on it. If this creature would leave the battlefield, if it has a death counter on it, exile it instead.)

Started out as a common with a rebirth cost of 3B. Was trying for a black Squadron Hawk.

FYI, the official rules for rebirth are as follows:

702.XX. Rebirth

702.XXa Rebirth represents two static abilities: one that functions while the card is in a player's graveyard and the other that functions while the card is on the battlefield. "Rebirth [cost]" means "You may cast this card from your graveyard by paying [cost] rather than paying its mana cost. If you do, this permanent enters the battlefield with a death counter on it" and "If this permanent would leave the battlefield, if it has a death counter on it, exile it instead of putting it anywhere else." Casting a spell using its rebirth ability follows the rules for paying alternative costs in rules 601.2b and 601.2e–g.

* Casting a card by using its rebirth ability works just like casting any other card except you're casting the card from your graveyard rather than your hand.

* A rebirth card cast from your graveyard follows the normal timing rules for creature cards.

* To cast a rebirth card from your graveyard, you must pay its rebirth cost.

* When a rebirth card you cast from your graveyard is countered, it's put back into your graveyard.

Having more information to choose a card type, therefore increasing the chance of choosing the card type that will be revealed, doesn't make it not random (double negative?)

But it's a moot point, because I've changed it to "...Shuffle your library, then reveal the top card..."

What's your definition of augur? (I think you may be thinking of auger.)

Updated original post with current wording. Here are some other sample cards:

Battlefield Teleportation
2W
Tribal Instant – Kithkin (Common)
Augur (When you cast this spell, choose a card type. Shuffle your library, then reveal the top card. If it shares a type with the chosen card type, put it into your hand. Otherwise, put it on the bottom of your library.)
Exile target creature. Return that card to the battlefield under its owner's control at the beginning of the next end step.

Merrow Sage
2U
Creature – Merfolk Wizard (Common)
1/1
T: Draw a card, then shuffle a card from your hand into your library.
Augur (When you cast this spell, choose a card type. Shuffle your library, then reveal the top card. If it shares a type with the chosen card type, put it into your hand. Otherwise, put it on the bottom of your library.)

Shock Therapy
1B
Sorcery (Uncommon)
Augur (When you cast this spell, choose a card type. Shuffle your library, then reveal the top card. If it shares a type with the chosen card type, put it into your hand. Otherwise, put it on the bottom of your library.)
Choose a card type other than land. Target player reveals his or her hand and you choose a card of that type from it. That player discards that card.

I don't see anyone cutting into the top three cards (or the bottom card), more like approximately half way through the library. Most if not all of those cards you mentioned, with the exception of Scroll Rack, only affect the top three cards or the bottom card of your library.

This keyword ability was created for a Mechanic Creator Contest with the challenge "design a mechanic that contains a word random!" (Cascade is currently the only printed mechanic with the word random.)

I started off with many variations, including one where you revealed a card at random from your hand (like Cursed Scroll).

It doesn't use the word random, but if I pursue this mechanic for the new tribal set I'm working on, I suppose I could change it to this:

Augur (When you cast this spell, choose a card type. Shuffle your library, then reveal the top card. If it shares a type with the chosen card type, put it into your hand. Otherwise, put it on the bottom of your library.)

I did ponder how one would reveal a card at random from his or her library. Probably just have an opponent cut into a card. Like having your opponent choose a card from your hand when his Hypnotic Specter deals combat damage to you... I don't know that one would "have to shuffle first" to reveal a card at random from their library.

I didn't initially have the shuffle afterwards either.  It was suggested that if you don't reveal a card that shares a type with the chosen card type, you have to put the revealed card back exactly where you found it, "which could also be easy to cheatyface if your opponent isn't paying close attention."

Shuffling afterwards minimizes looking at extra cards tournament violations or other cheats.

***Keyword Ability: Augur***

Augur is a triggered ability that may let a player put a random card from his or her library into his or her hand.

Concussion Blast
1R
Instant (Uncommon)
Augur (When you cast this spell, choose a card type. Reveal a card at random from your library. If it shares a type with the chosen card type, put it into your hand. Then shuffle your library.)
Concussion Blast deals 2 damage to target creature or player.

The official rules for augur are as follows:

702.XXa Augur is a triggered ability that functions only while the spell with augur is on the stack. "Augur" means "When you cast this spell, choose a card type. Reveal a card at random from your library. If the card revealed this way shares a type with the chosen card type, put it into your hand. Then shuffle your library."

* On instant and sorcery cards, the augur ability is printed first; on permanent cards, the augur ability is printed last. Regardless of the card type, augur triggers when the spell is cast, not when it resolves (that is, before the permanent would enter the battlefield).

* Here's the timing for augur:
1) You cast a spell with augur.
2) The augur ability triggers and goes on the stack on top of the original spell. You choose a card type.
3) The augur ability resolves. Reveal a card at random from your library. If you reveal a card that shares a type with the chosen card type, put it into your hand. Then shuffle your library.
4) The original spell resolves.

* Countering the original spell doesn't counter the augur ability.

* Since augur is a triggered ability, anything that interacts with a triggered ability (such as Stifle) will interact with augur.

Current Wording:

***Keyword Ability: Augur***

Augur is a triggered ability that may let a player put a random card from his or her library into his or her hand.

Concussion Blast
1R
Instant (Uncommon)
Augur (When you cast this spell, choose a card type. Shuffle your library, then reveal the top card. If it shares a type with the chosen card type, put it into your hand. Otherwise, put it on the bottom of your library.)
Concussion Blast deals 2 damage to target creature or player.

The official rules for augur are as follows:

702.XX. Augur

702.XXa Augur is a triggered ability that functions only while the spell with augur is on the stack. "Augur" means "When you cast this spell, choose a card type. Shuffle your library, then reveal the top card. If the card revealed this way shares a type with the chosen card type, put it into your hand. Otherwise, put it on the bottom of your library."

* On instant and sorcery cards, the augur ability is printed first; on permanent cards, the augur ability is printed last. Regardless of the card type, augur triggers when the spell is cast, not when it resolves (that is, before the permanent would enter the battlefield).

* Here's the timing for augur:
1) You cast a spell with augur.
2) The augur ability triggers and goes on the stack on top of the original spell. You choose a card type.
3) The augur ability resolves. Shuffle your library, then reveal the top card. If you reveal a card that shares a type with the chosen card type, put it into your hand. Otherwise, put it on the bottom of your library.
4) The original spell resolves.

* Countering the original spell doesn't counter the augur ability.

* Since augur is a triggered ability, anything that interacts with a triggered ability (such as Stifle) will interact with augur.

Thanks!

There was some concern over bounce if you spent red. (That this only appeared in red in Planar Chaos.) I think red can have a small amount of "return target creature an opponent controls to its owner's hand", plus you need to spend blue to cast Scyphozoa.

* As a Goblins player, one of my happiest days was when WoTC printed Stingscourger for my Goblin deck. It gave me a way to deal with Darksteel Colossus...

New:

Scyphozoa
3U
Creature – Jellyfish (Common)
2/2
Scyphozoa can't be blocked except by blue creatures.
When Scyphozoa enters the battlefield, if R was spent to cast Scyphozoa, return target creature an opponent controls to its owner's hand.

Centaur Stargazer
3G
Creature – Centaur Archer (Common)
2/3
Reach
When Centaur Stargazer enters the battlefield, if U was spent to cast Centaur Stargazer, look at the top four cards of your library, then put them back in any order.

Updated rebirth based on feedback from AmbivalentDuck. Rebirth cost is now about 2 mana more than casting cost...

For example:

Arboreal Guardian
G
Creature – Elf Druid (Common)
1/1
Sacrifice Arboreal Guardian: Search your library for a basic land card, reveal it, and put it into your hand. Then shuffle your library.
Rebirth 2G (You may cast this card from your graveyard for its rebirth cost. If you do, it enters the battlefield with a death counter on it. If this creature would leave the battlefield, if it has a death counter on it, exile it instead.)

Vengeful Aven
2W
Creature – Bird Soldier (Common)
2/2
Flying
Vengeful Aven has first strike as long as it has a death counter on it.
Rebirth 4W (You may cast this card from your graveyard for its rebirth cost. If you do, it enters the battlefield with a death counter on it. If this creature would leave the battlefield, if it has a death counter on it, exile it instead.)

Updated first post.

At best, Ring of Ice is:

2 to cast, U to equip to a creature, 1 to tap equipped creature and tap an artifact, creature, or land, and 1U for each additional untapped creature you control to tap an artifact, creature, or land.

That is not quite the same as 2UU, tap an untapped creature you control: Tap target artifact, creature, or land.

Whereas Opposition could tap, for example, 4 permanents for 2UU, Ring of Ice would need 6UUUU to tap 4 permanents.  Without blue mana you would need 14 mana to tap four permanents.

And artifacts are easier to deal with than enchantments.

Added second card in cycle:

Ring of Ice
2
Artifact - Equipment (Uncommon)
Equipped creature has "1, T: Tap target artifact, creature, or land."
U: Attach Ring of Ice to target creature you control.
Equip 2 (2: Attach to target creature you control. Equip only as a sorcery.)

Uncommon it is.

Dwarven Pioneer is being changed to:

Wandering Giant
3R
Creature – Giant Nomad (Common)
3/3
When Wandering Giant enters the battlefield, if W was spent to cast Wandering Giant, you may search your library for a Plains card, put it onto the battlefield tapped, then shuffle your library.

Seems more appropriate...

What would you change about the costing of the mechanic? I can provide examples of other cards with rebirth...

Rebirth (originally named reanimate) was conceived as flashback for creatures and I also drew inspiration from Bogardan Phoenix. It was created back in 2007 and I have found the threads where I posted cards with reanimate on www.mtgnews.com, www.mtgsalvation.com, and here. These posts predate both persist (2008) and unearth (2008). I do remember using Haakon, Stromgald Scourge (2006) as a reference...

Yes, your opponent can just tap all their lands at the end of their turn to prevent you from syphoning their mana on your turn (only creature, enchantment, and sorcery cards have syphon), but not if they want to play instants or other reactive spells... Cancel, Holy Day, Vines of Vastwood, etc.

I also have cards in my set that circumvent opponents with tapped lands. For example, the Explorer cycle:

Tireless Explorer
1W
Creature – Human Soldier Scout (Common)
1/1
T, Untap a tapped land an opponent controls: Add one mana of any type that land could produce to your mana pool.
Rebirth 1W (You may cast this card from your graveyard for its rebirth cost. If you do, it enters the battlefield with a death counter on it. When this creature leaves the battlefield, if it had a death counter on it, exile it.)

Ceaseless Explorer
1U
Creature – Merfolk Scout (Common)
1/1
T, Untap a tapped land an opponent controls: Add one mana of any type that land could produce to your mana pool.
Rebirth 1U (You may cast this card from your graveyard for its rebirth cost. If you do, it enters the battlefield with a death counter on it. When this creature leaves the battlefield, if it had a death counter on it, exile it.)

Restless Explorer
1B
Creature – Zombie Scout (Common)
1/1
T, Untap a tapped land an opponent controls: Add one mana of any type that land could produce to your mana pool.
Rebirth 1B (You may cast this card from your graveyard for its rebirth cost. If you do, it enters the battlefield with a death counter on it. When this creature leaves the battlefield, if it had a death counter on it, exile it.)

Reckless Explorer
1R
Creature – Dwarf Scout (Common)
1/1
T, Untap a tapped land an opponent controls: Add one mana of any type that land could produce to your mana pool.
Rebirth 1R (You may cast this card from your graveyard for its rebirth cost. If you do, it enters the battlefield with a death counter on it. When this creature leaves
the battlefield, if it had a death counter on it, exile it.)

Dauntless Explorer
1G
Creature – Elf Druid Scout (Common)
1/1
T, Untap a tapped land an opponent controls: Add one mana of any type that land could produce to your mana pool.
Rebirth 1G (You may cast this card from your graveyard for its rebirth cost. If you do, it enters the battlefield with a death counter on it. When this creature leaves the battlefield, if it had a death counter on it, exile it.)

I find it amusing when people don't know how regeneration works.

Crosswind Drake enters the battlefield with a regeneration shield. If Crosswind Drake would be destroyed (say, beacause it flashed into play and blocked a 2/2 creature), instead remove all damage from it and tap it...


Touché.  Or like Flashback and Retrace?

Skeletal Warriors
3B
Creature – Skeleton Warrior (Common)
3/1
When Skeletal Warriors enters the battlefield, if its rebirth cost was paid, sacrifice a creature.
B: Regenerate Skeletal Warriors.
Rebirth B (You may cast this card from your graveyard for its rebirth cost. If you do, it enters the battlefield with a death counter on it. If this creature would leave the battlefield, if it has a death counter on it, exile it instead.)

Abnegate
U
Instant (Common)
As an additional cost to cast Abnegate, sacrifice a nonland permanent.
Return target permanent to its owner's hand.

Banish
4W
Sorcery (Common)
Syphon 2 (As you cast this spell, tap up to two untapped lands you don't control. Each land tapped this way reduces this spell's cost by 1 or by one mana of any color that land could produce.)
If you control a Plains, put target creature on top of its owner's library.

Anarchic Satyr
BR
Creature – Satyr (Common)
2/2
T: Target creature gains plainswalk until end of turn.

Repudiate
UU
Instant (Common)
Counter target creature spell. If that spell is countered this way, exile it instead of putting it into its owner's graveyard.

Peridot Gemstone
1
Artifact (Common)
Peridot Gemstone enters the battlefield with two charge counters on it.
T, Remove a charge counter from Peridot Gemstone: Add G to your mana pool.

Dwarven Pioneer
3R
Creature – Dwarf Nomad (Common)
2/4
When Dwarven Pioneer enters the battlefield, if W was spent to cast Dwarven Pioneer, you may search your library for a Plains card, put it onto the battlefield tapped, then shuffle your library.

Cripple
B
Instant (Common)
As an additional cost to cast Cripple, sacrifice a nonland permanent.
Target creature gets -4/-4 until end of turn.

Fierce Gull
1U
Creature – Bird (Common)
2/2
Flying
At the beginning of your upkeep, put the top two cards of your library into your graveyard.

Wreck
2G
Sorcery (Common)
Syphon 2 (As you cast this spell, tap up to two untapped lands you don't control. Each land tapped this way reduces this spell's cost by 1 or by one mana of any color that land could produce.)
If you control a Forest, destroy target artifact or enchantment.

Horizon Walker
2WW
Creature – Human Wizard (Uncommon)
2/3
Plainswalk
Whenever Horizon Walker deals damage to a player, you may exile another target permanent. If you do, return that card to the battlefield under its owner's control at the beginning of the next end step.

Goblin Rabble
R
Creature – Goblin Warrior (Uncommon)
1/1
Sacrifice Goblin Rabble: Creatures you control get +1/+0 until end of turn.
Rebirth R (You may cast this card from your graveyard for its rebirth cost. If you do, it enters the battlefield with a death counter on it. If this creature would leave the battlefield, if it has a death counter on it, exile it instead.)

Arcane Initiate
1UU
Creature – Human Wizard (Uncommon)
2/2
T: Counter target spell or activated ability unless its controller pays 1. (Mana abilities can't be targeted.)

Revered Lammasu
4WW
Creature – Lammasu (Mythic Rare)
5/5
Ward against black and against red (This card can't be the target of black or red spells or abilities from black or red sources, even if this card isn't on the battlefield.)
Flying
At the beginning of each player's end step, untap all creatures you control.

Mountain
Basic Land - Mountain
(T: Add R to your mana pool.)

Vengeful Aven
2W
Creature - Bird Soldier (Common)
2/2
Flying
Vengeful Aven has first strike as long as it has a death counter on it.
Rebirth 3W (You may cast this card from your graveyard for its rebirth cost. If you do, it enters the battlefield with a death counter on it. If this creature would leave the battlefield, if it has a death counter on it, exile it instead.)

Necropsy
1B
Sorcery (Common)
As an additional cost to cast Necropsy, exile a creature card from your graveyard.
Draw two cards.

Tanzanite Gemstone
1
Artifact (Common)
Tanzanite Gemstone enters the battlefield with two charge counters on it.
T, Remove a charge counter from Tanzanite Gemstone: Add U to your mana pool.

Dauntless Explorer
1G
Creature - Elf Druid Scout (Common)
1/1
T, Untap a tapped land an opponent controls: Add one mana of any type that land could produce to your mana pool.
Rebirth 1G (You may cast this card from your graveyard for its rebirth cost. If you do, it enters the battlefield with a death counter on it. If this creature would leave the battlefield, if it has a death counter on it, exile it instead.)

Crosswind Drake
3U
Creature - Drake (Common)
3/1
Flash
Flying
When Crosswind Drake enters the battlefield, if G was spent to cast Crosswind Drake, regenerate it.

Shieldwall Soldier
1W
Creature - Human Soldier (Common)
1/2
T: Target unblocked attacking creature with plainswalk becomes blocked. Activate this ability only during combat after blockers are declared.
Cycling W (W, Discard this card: Draw a card.)

Foraging Gerenuk
2G
Creature - Antelope (Common)
2/2
At the beginning of your end step, if you control no untapped lands, you may gain 2 life.

Drag to Hell
1BB
Instant (Common)
Destroy target nonblack creature, then exile a nonblack creature card from a graveyard.

Goblin Skirmisher
R
Creature - Goblin Warrior (Common)
2/2
Whenever Goblin Skirmisher attacks, return target Goblin creature to its owner's hand.

Wisplight Lynx
GW
Creature - Cat Spirit (Common)
2/2
T: Target creature gains swampwalk until end of turn.

Reviving Circlet
2
Artifact - Equipment (Uncommon)
Equipped creature has "1: Regenerate this creature."
G: Attach Reviving Circlet to target creature you control.
Equip 1 (1: Attach to target creature you control. Equip only as a sorcery.)

Bloodthirsty Vampire
3BB
Creature - Vampire Warrior (Uncommon)
4/3
Flying
Rebirth–Sacrifice two creatures. (You may cast this card from your graveyard for its rebirth cost. If you do, it enters the battlefield with a death counter on it. If this creature would leave the battlefield, if it has a death counter on it, exile it instead.)

Pyroclastic Surge
2RR
Sorcery (Uncommon)
Syphon 2 (As you cast this spell, tap up to two untapped lands you don't control. Each land tapped this way reduces this spell's cost by  or by one mana of any color that land could produce.)
If you control a Mountain, Pyroclastic Surge deals 2 damage to each creature and each player.

Jagged Foothills
Land - Mountain Forest (Rare)
(T: Add R or G to your mana pool.)
When Jagged Foothills enters the battlefield, target opponent may search his or her library for a basic land card, reveal it, and put it into his or her hand. If that player does, he or she then shuffles his or her library.

Plains
Basic Land - Plains
(T: Add W to your mana pool.)

My set has a cycle of 10 "enhanced" creatures (some monocolored creatures in my set have a bigger effect if mana of a specific color was used to pay their costs). Here's what I have so far:

Borderland Zealot
3W
Creature – Human Soldier (Common)
2/4
When Borderland Zealot enters the battlefield, if B was spent to cast Borderland Zealot, target creature gets -1/-1 until end of turn.

Exotic Weapon Master
3W
Creature - Human Soldier (Common)
2/2
Flash
When Exotic Weapon Master enters the battlefield, if R was spent to cast Exotic Weapon Master, it gains haste until end of turn.
T: Tap target creature.

Crosswind Drake
3U
Creature – Drake (Common)
3/1
Flash
Flying
When Crosswind Drake enters the battlefield, if G was spent to cast Crosswind Drake, regenerate it.

Dwarven Pioneer
3R
Creature – Dwarf Nomad (Common)
2/4
When Dwarven Pioneer enters the battlefield, if W was spent to cast Dwarven Pioneer, you may search your library for a Plains card, put it onto the battlefield tapped, then shuffle your library.

Streetwise Scoundrels
3R
Creature – Human Rogue (Common)
3/1
First strike
When Streetwise Scoundrels enters the battlefield, if U was spent to play Streetwise Scoundrels, each opponent sacrifices a permanent unless he or she pays 1.

I like my cycle.

Love Magus of the Needle!

I wanted to complete this cycle of equipment, but I don`t think I`ll have time before the deadline:

Reviving Circlet
2
Artifact – Equipment (Common)
Equipped creature has "1: Regenerate this creature."
G: Attach Reviving Circlet to target creature you control.
Equip 1 (1: Attach to target creature you control. Equip only as a sorcery.)

Razor Construct

Artifact Creature – Cleric (Common)
1/1
, Sacrifice Razor Construct: Target permanent you control gains protection from artifacts until end of turn.

Quicksilver Construct

Artifact Creature – Wizard (Common)
1/1
, Sacrifice Quicksilver Construct: Proliferate. (You choose any number of permanents and/or players with counters on them, then give each another counter of a kind already there.)

Mephidross Construct

Artifact Creature – Shaman (Common)
1/1
, Sacrifice Mephidross Construct: Remove all counters from target artifact or creature.

Oxidda Construct

Artifact Creature – Warrior (Common)
1/1
, Sacrifice Oxidda Construct: Destroy target artifact.

Tangle Construct

Artifact Creature – Scout (Common)
1/1
, Sacrifice Tangle Construct: Prevent all combat damage that would be dealt this turn.

Yes, I am a fan of anime such as Ghost in the Shell, Akira, Ninja Scroll, Princess Mononoke, and Spirited Away...

Reviving Circlet
2
Artifact – Equipment (Common)
Equipped creature has "1: Regenerate this creature."
G: Attach Reviving Circlet to target creature you control.
Equip 1 (1: Attach to target creature you control. Equip only as a sorcery.)

Should this be an Uncommon? It is possible to set up regeneration shields on multiple creatures at instant speed... compare with Nurturing Licid (Uncommon), Refresh (Common), Regenerate (Common), Regeneration (Uncommon), Reknit (Uncommon), Resuscitate (Uncommon), Wrap in Vigor (Common)... and also Herbal Poultice (Common)...

OK by me.

With rebirth as an activated ability, I could add one or more of the following hosers to my set:

Vigilant Bailiff
1WW
Creature – Human Knight (Rare)
2/2
Activated abilities of cards not in play can't be activated.

Or

Nullstone
4
Artifact (Rare)
Activated abilities of cards not in play can't be activated.

Arcane Initiate
1UU
Creature – Human Wizard (Uncommon)
2/2
T: Counter target spell or activated ability unless its controller pays 1. (Mana abilities can't be targeted.)

Entranced Shaman
RR
Creature – Human Shaman (Rare)
2/1
Sacrifice Entranced Shaman: Until end of turn, other players can't play cards from their graveyards, and you may play cards from other players' graveyards as though they were in your graveyard.
Rebirth 3R (3R: Return this card from your graveyard to the battlefield with a death counter on it. If this creature would leave the battlefield, if it has a death counter on it, exile it instead. Rebirth only as a sorcery.)