On opponents turn I chump blocked to trigger Archangel Avacyn's transform on my upkeep.
Opponent has Giltspire Avenger on the battlefield, and Faith's Shield in hand. Is it possible for him to cast it for pro-red, before Avacyn's transform into purifierPurifier deals it lethal damage?
If so and even if not so, does the 3 damage Avacyn does to opponent allow Giltspire to tap and destroy it?