Knowledge Pool: Help me wade through it!

[ReubenG]

Knowledge Pool
Artifact
Imprint -- When Knowledge Pool enters the battlefield, each player exiles the top three cards of his or her library.
Whenever a player casts a spell from his or her hand, that player exiles it. If the player does, he or she may cast another nonland card exiled with Knowledge Pool without paying that card's mana cost.


I would like to discuss some of the rules with Knowledge Pool as I am not sure I fully grasp how this card affects game states, though maybe I do and this can be helpful to others.  I will start with this question and add more if needed. 

I get the imprint ability, that makes sense, but what about after Knowledge Pool resolves and we have 6 cards “in the pool”

There are 2 more triggered abilities on this card:

The “exile spell” ability: “Whenever a player casts a spell from his or her hand, that player exiles it.”

And the “Play Free” ability: “If the player does, he or she may cast another nonland card exiled with Knowledge Pool without paying that card's mana cost.”


Now I understand that once I have resolved Knowledge Pool (Or tinkered into play) as the Active Player I will receive priority and can then cast the first spell “into the pool”.

From what I understand the "exile spell" triggered ability is triggered and put on the stack when I cast the spell, not when it resolves, and then the third ability triggers and is put onto the stack. Then if I don’t cast another spell, priority passes and my opponent can then do the same.

So what I am not fully clear on is this from the FAQ for Mirrodin Besieged:

If the original spell isn't exiled (perhaps because it's countered by another spell or ability before Knowledge Pool's second triggered ability resolves), the rest of the ability does nothing. The player doesn't get to cast an exiled card.

This makes it sound like any spell cast, can be countered before the second exile ability resolves, never triggering the third play free ability.  But wouldn’t this “counterspell” be exiled with knowledge pool before it can resolve and need to be a counter spell cast from the pool?

For Example: 
Knowledge Pool resolves.
Imprint ability resolves and Exiles: (Land, FOW, Jace2.0, Land , Nature’s Claim, Yawgmoth’s Will)
I get priority (since Imprint was not responded to) and then cast Mox Jet, opponent responds with Spell Pierce targeting Mox Jet.

Stack:
Mox Jet
Exile Jet
Spell Pierce targeting Mox Jet
Exile Spell Pierce

Wouldn’t the Exile Spell Pierce ability resolve first not allowing Spell Pierce to resolve and counter Mox Jet?  Or does the exiling happen after the casting of the spell prior to priority passing?  If so how could you counter the Mox Jet if it’s not on the stack to counter?

If that is correct they must be talking about, the exile ability resolving triggering the third “play for free” ability.  So it would look like this:

Mox Jet
Exile Jet
Spell Pierce targeting Mox Jet
Exile Spell Pierce

Exile Spell Pierce Resolves, triggers “play free ability”, exiles Spell Pierce from stack into the pool.

Stack now:
Mox Jet
Exile Jet
“play free” Opponent chooses FOW targeting Mox Jet

FOW resolves countering Mox Jet and removing from stack to my graveyard since it is not exiled by knowledge pool) and Exile Jet has an illegal target and I don’t trigger the third play free ability.

Is that the correct way it works?

If it does work that way then am I correct that I could then counter the FOW with the Spell Pierce used to cast FOW from the Pool?

Here is that example (after Spell Pierce used to cast FOW from Pool):

Stack:
Mox Jet
Exile Jet
FOW targeting Mox Jet (played from pool by Spell Pierce getting exiled)

Pool is now (Land, Jace2.0, Land , Nature’s Claim, Yawgmoth’s Will, Spell Pierce)

I then respond to the casting of FOW from the pool by my opponent and by casting my own instant (let’s say steel sabotage targeting an opponent’s tapped Mox Pearl) Can I then counter the FOW?  Stack would look like this:

Mox Jet
Exile Jet
FOW targeting Mox Jet (played from pool by Spell Pierce getting exiled)
Steel Sabotage targeting Mox Pearl
Exile Steel Sabotage

Exile Steel Sabotage resolves, Steel sabotage is exiled into pool, and then I chose to cast Spell Pierce targeting FOW. 

Mox Jet
Exile Jet
FOW targeting Mox Jet (played from pool by Spell Pierce getting exiled)
Spell Pierce targeting FOW

Spell Pierce resolves countering FOW and moving into the original owner’s graveyard, and leaves:

Mox Jet
Exile Jet

Exile Mox Jet resolves, removing it from the stack to the pool, and triggering the third play free ability.

Play free ability targeting Jace2.0

I end up all of this with a Jace 2.0 and a pool with (Land, Land, Nature’s Claim, Yawgmoth’s Will, Steel Sabotage, and Mox Jet)

Do I understand this correctly?

[Clariax]

Seems there's a few misunderstandings here.  First off all, Knowledge Pool has 2 abilities, not 3.

  "Whenever a player casts a spell from his or her hand, that player exiles it. If the player does, he or she may cast another nonland card exiled with Knowledge Pool without paying that card's mana cost."

is all a single ability, not 2 separate ones. 

The second misunderstanding seems to be with the idea of the spell being countered before it gets exiled.  If someone responds to the triggered ability by casting a counterspell (or spell pierce), this would cause Knowledge Pool to trigger again.  However, there are other ways a spell can get countered without casting another spell.  Various activated and triggered abilities can counter spells.  For example, you could cast a spell, then while Knowledge Pool's trigger is on the stack, the spell could get countered with Voidmage Prodigy's activated ability.  Then when Knowledge Pool's trigger resolves, the spell isn't on the stack anymore so can't get exiled, so the "If the player does" clause never happens.

[ReubenG]

Seems there's a few misunderstandings here.  First off all, Knowledge Pool has 2 abilities, not 3.

  "Whenever a player casts a spell from his or her hand, that player exiles it. If the player does, he or she may cast another nonland card exiled with Knowledge Pool without paying that card's mana cost."

is all a single ability, not 2 separate ones.  

The second misunderstanding seems to be with the idea of the spell being countered before it gets exiled.  If someone responds to the triggered ability by casting a counterspell (or spell pierce), this would cause Knowledge Pool to trigger again.  However, there are other ways a spell can get countered without casting another spell.  Various activated and triggered abilities can counter spells.  For example, you could cast a spell, then while Knowledge Pool's trigger is on the stack, the spell could get countered with Voidmage Prodigy's activated ability.  Then when Knowledge Pool's trigger resolves, the spell isn't on the stack anymore so can't get exiled, so the "If the player does" clause never happens.

Thank you for the reply that clears up some things.  So let me go through this so I am clear.

Back to the example:  
Knowledge Pool resolves.
Imprint ability resolves and Exiles: (Land, FOW, Jace2.0, Land , Nature’s Claim, Yawgmoth’s Will)
I get priority (since Imprint was not responded to) and then cast Mox Jet, opponent responds to Knowledge Pools Exile, if so play free ability by casting Spell Pierce from their hand targeting Mox Jet which then triggers knowledge pool's ability again.  

Stack:
Mox Jet
Exile Jet, if so play spell from pool free
Spell Pierce targeting Mox Jet
Exile Spell Pierce, if so play spell from pool free

I don't responde, so Exile Spell Pierce resolves, exiling Spell Pierce and my opponent can then cast a non-land spell from the pool for free placving it on the stack.

Can my opponent chose to cast FOW from the pool for free targeting Mox Jet, and therefore the Knowledge Pool ability triggered by casting the Jet when it resolves has no legal target to exile and I don’t get to cast a spell from the pool for free?

If my opponent can counter the Jet with FOW from the pool, can I then respond to the FOW by casting another instant from my hand to trigger Knowledge Pool and counter FOW with the Spell Pierce put into the pool to cast FOW?

[Clariax]

You're correct about all of that except for one minor detail.

Can my opponent chose to cast FOW from the pool for free targeting Mox Jet, and therefore the Knowledge Pool ability triggered by casting the Jet when it resolves has no legal target to exile and I don’t get to cast a spell from the pool for free?

Knowledge Pool's triggered ability doesn't target.  It simply exiles the spell that triggered it (or at least attempts to exile it), it doesn't actually target that spell.

[ReubenG]

You're correct about all of that except for one minor detail.

Can my opponent chose to cast FOW from the pool for free targeting Mox Jet, and therefore the Knowledge Pool ability triggered by casting the Jet when it resolves has no legal target to exile and I don’t get to cast a spell from the pool for free?

Knowledge Pool's triggered ability doesn't target.  It simply exiles the spell that triggered it (or at least attempts to exile it), it doesn't actually target that spell.

Thank you for the reply and pointing out that detail, those minor details are important to rules.

A few other details on Knowledge Pool that I want to make sure I have straight:

First, if a spell that has the storm ability is cast from a players hand with a Knowledge Pool on the battlefield, from what I understand both the Knowledge Pool ability and Storm copies will be put on the stack in Active Player/ Non Active Player order, and the storm count would be all spells cast (not resolved) before the storm ability spell (including those exiled by Knowledge Pool and cast for free from the of the pool of exiled cards) since the storm ability requires the Storm Spell to be cast not resolved (even though it is exiled by Knowledge Pool) to trigger the storm ability.

Second, if Knowledge Pool is removed from the battlefield, all the spells exiled by Knowledge Pool's Imprint ability will remain exiled, and if Knowledge Pool re-enters the battlefield it is a new copy which will trigger the imprint ability and exile 6 new cards that the second ability references to and doesn’t refer back to any cards exiled by the previous Knowledge Pool.

[Clariax]

First, if a spell that has the storm ability is cast from a players hand with a Knowledge Pool on the battlefield, from what I understand both the Knowledge Pool ability and Storm copies will be put on the stack in Active Player/ Non Active Player order, and the storm count would be all spells cast (not resolved) before the storm ability spell (including those exiled by Knowledge Pool and cast for free from the of the pool of exiled cards) since the storm ability requires the Storm Spell to be cast not resolved (even though it is exiled by Knowledge Pool) to trigger the storm ability.

Storm is a triggered ability that triggers when the spell it's on is cast.  On resolution of that trigger, it creates copies for each spell cast that turn before the storm spell.  It's important to note that it's each spell cast before the spell with storm was cast.  It is not the number of spells cast before the storm trigger resolves.  So once the storm spell has been cast, the number of copies the trigger will make is locked in.  Also the storm ability will create copies even if the spell that triggered it is no longer on the stack.

Second, if Knowledge Pool is removed from the battlefield, all the spells exiled by Knowledge Pool's Imprint ability will remain exiled, and if Knowledge Pool re-enters the battlefield it is a new copy which will trigger the imprint ability and exile 6 new cards that the second ability references to and doesn’t refer back to any cards exiled by the previous Knowledge Pool.

Any cards in the exile zone when Knowledge Pool leaves the battlefield will remain there.  And a new Knowledge Pool entering the battlefield at some later point is an entirely new object, even if it's represented by the same physical piece of cardboard.  Each Knowledge Pool refers specifically to cards exiled by its own abilities, and not any cards exiled by other Knowledge Pools.

[ReubenG]

First, if a spell that has the storm ability is cast from a players hand with a Knowledge Pool on the battlefield, from what I understand both the Knowledge Pool ability and Storm copies will be put on the stack in Active Player/ Non Active Player order, and the storm count would be all spells cast (not resolved) before the storm ability spell (including those exiled by Knowledge Pool and cast for free from the of the pool of exiled cards) since the storm ability requires the Storm Spell to be cast not resolved (even though it is exiled by Knowledge Pool) to trigger the storm ability.

Storm is a triggered ability that triggers when the spell it's on is cast.  On resolution of that trigger, it creates copies for each spell cast that turn before the storm spell.  It's important to note that it's each spell cast before the spell with storm was cast.  It is not the number of spells cast before the storm trigger resolves.  So once the storm spell has been cast, the number of copies the trigger will make is locked in.  Also the storm ability will create copies even if the spell that triggered it is no longer on the stack.

Second, if Knowledge Pool is removed from the battlefield, all the spells exiled by Knowledge Pool's Imprint ability will remain exiled, and if Knowledge Pool re-enters the battlefield it is a new copy which will trigger the imprint ability and exile 6 new cards that the second ability references to and doesn’t refer back to any cards exiled by the previous Knowledge Pool.

Any cards in the exile zone when Knowledge Pool leaves the battlefield will remain there.  And a new Knowledge Pool entering the battlefield at some later point is an entirely new object, even if it's represented by the same physical piece of cardboard.  Each Knowledge Pool refers specifically to cards exiled by its own abilities, and not any cards exiled by other Knowledge Pools.

Thank you for the reply.