2010-06-15 : Annihilator abilities trigger and resolve during the declare attackers step. The defending player chooses and sacrifices the required number of permanents before they declare blockers. Any creatures sacrificed this way won’t be able to block.

2010-06-15 : Eldrazi Conscription is an Eldrazi. However, it doesn’t turn the enchanted creature into an Eldrazi.

2010-06-15 : If a creature with annihilator is attacking a planeswalker, and the defending player chooses to sacrifice that planeswalker, the attacking creature continues to attack. It may be blocked. If it isn’t blocked, it simply won’t deal combat damage to anything.

2018-12-07 : If a creature has multiple instances of annihilator, each triggers separately when that creature attacks.