Collectible Card Game Headquarters

Describe the Bug:
When Ulamog, the Infinite Gyre attacks and its controller controls Ulamog, the Ceaseless Hunger, the latter's triggered ability triggers and defending player exiles the top twenty cards of his/her library.

Which card did behave improperly ?
Ulamog, the Ceaseless Hunger

Which update are you using?(date,name)Which type(Duel,Gauntlet,Sealed Deck)
BfZv2, Gauntlet

What exactly should be the correct behavior/interaction ?
Ulamog, the Ceaseless Hunger's triggered ability only triggers when Ulamog, the Ceaseless Hunger attacks.

Are any other cards possibly affected by this bug ?
-

(possible culprit: interference from Ulamog, the Ceaseless Hunger's etbcast trigger - DAT_STORE_IN_INFO_SLOT might help)

Can anyone get it to trigger if something besides the other Ulamog attacks?

You are right, Infinite Gyre is not the only one triggering it. Kozilek, Butcher of Truth does it too

Just annihilators? Or just other cards with attack triggers? Never mind, it's definitely a storage clash with the cast trigger. Bug manifests if the second exiled permanent is the AI's, and doesn't if it's the human's or the cast trigger never happens.

Ankle Shanker and Alaborn Cavalier, too. So probably attack triggers.

Akroan Hoplite and Anafenza, the Foremost are not affected, though. guessing those use a different kind of trigger?

Regarding your edit, Akroan Hoplite and Anafenza, the Foremost don't trigger it when the second exiled permanent (or both) were AI's.

Well, apparently they do, but didn't when I first tested them despite always exiling the same two permanents in the same savegame.

Fixed 779a746.