[confirmed]Ashiok, Nightmare Weaver - stack problem

[BAgate]

Describe the Bug:
If you try to use Ashiok, Nightmare Weaver 's 2nd ability and in response Ashiok is dealt lethal damage the nightmare creature is never created.

Which card did behave improperly ?
Ashiok, Nightmare Weaver

Which update are you using?(date,name)Which type(Duel,Gauntlet,Sealed Deck)
Manalink 2015/3/25: Fate Reforged,duel

What exactly should be the correct behavior/interaction ?
Once the ability is on the stack the state of the source is irrelevant.

Are any other cards possibly affected by this bug ?
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[Aswan jaguar]

Confirmed.The same happens if you use all loyalty as x for the creature's converted mana cost and Ashiok, Nightmare Weaver goes to gy as a result no nightmare creature is created.

[Korath]

What's happening here is that the effect card tracking the exiled creatures gets destroyed when Ashiok leaves the battlefield, so when the ability tries to check that there's still a creature card of the appropriate name exiled by Ashiok during resolution, it thinks it's already gone.

The family of effect cards that keep track of this data have an interface to let them become detached from their source card, so that they can be used by e.g. instants or sorceries, or by abilities with "sacrifice this permanent" as part of their cost, but it's not set up to be easily mixed with the non-detached version.

However, since card instances don't get reused until the start of a new turn, the effect card is still accessible, just slightly harder to find. (Over on the Shandalar side of things, I exploit this for all the cards looking for a target "that was dealt damage this turn" - I look for fully-resolved and -destroyed damage cards, rather than trying to keep track of which cards have been dealt damage just in case some other card that may not even be in a library yet needs to check it later.) So probably the least-effort way to fix this is to make the function searching for the effect card at resolution still see the destroyed copies of those effects, and to doublecheck that, when those effects intentionally destroy themselves (perhaps because all the cards they were tracking are no longer in exile) that they mark themselves as having actually released all their cards.