Portal and dredge

[Moxlotus]

Can I dredge off a Bazaar if my opponent has a Possessed Portal in play?  What about off my draw phase?

[Khahan]

Can I dredge off a Bazaar if my opponent has a Possessed Portal in play?  What about off my draw phase?

Dredge is a replacement effect. It replaces any draw with putting N cards from your library into your graveyard to return the card to your hand.

[card]possessed portal[/card] also has a replcement effect that replaces card drawing. Since you would be the 'controller' of the affected card draw, you may choose which replacement effect to use. If you  use the dredge, then there is no card draw for possessed portal to replace. If you use the portal, then there is no draw for dredge to replace.

419.9a If two or more replacement or prevention effects are attempting to modify the way an event affects an object or player, the affected object's controller (or its owner if it has no controller) or the affected player chooses one to apply. Then the other effect applies if it is still appropriate. If one or more of the applicable replacement effects is a self-replacement effect (see rule 419.6d), that effect is applied before any other replacement effects. If two or more players have to make these choices at the same time, choices are made in APNAP order (see rule 103.4).
Example: Two permanents are in play. One is an enchantment that reads "If a card would be put into a graveyard, instead remove it from the game," and the other is a creature that reads "If [this creature] would be put into a graveyard from play, instead shuffle it into its owner's library." The controller of the creature that would be destroyed decides which replacement to apply first; the other does nothing.

[Harlequin]

the short answer is yes

a draw is about to resolve you get the follow choices:
- Draw nothing instead
- Dredge instead

You can also dredge instead of Uba mask choices look like:
- Remove top card, play it until end of turn (uba mask)
- Dredge instead

You could event have all 3, Plus Magara's Tomb! or words of wind!  But alas only one replacement effect will take effect. The choice lies with person controling the event.

[Lunar]

Dont forget that you still have to discard after the bazaar though...so if you are an ichorid deck you are okay, but others maybe not so good...heh

[Harlequin]

Dont forget that you still have to discard after the bazaar though...so if you are an ichorid deck you are okay, but others maybe not so good...heh

100% true.  Don't forget that just because 3 cards went to the yard, means you wont have to discard 3 cards afterwords.  But your draw for turn can be replaced with a dredge... perhapse buying time against the portal.

However.  You can replace all three draws Sylvan Library (2 added + 1 for turn) with 3 dredge cards and not need to pay any life or put any cards back ontop of your libraryt.  I'm 100% what the current wording/ruleing is, so my only justification of that is "the errata says so." It's pritty nifty tech, but you won't be able to keep that up for long before you deck yourself.

[Godder]

Sylvan Library refers to cards drawn during the Draw Step. If you don't 'draw' any cards, you don't have to put them back. Anything that replaces a draw with something that puts cards into hand or similar e.g. Abundance (old-school tech), Dredge, Uba Mask etc. will do the trick.