I was able to kill an opponent with Sephiroth's ability even though they had hexproof from black. Is this an Arena issue or am I missing something about the rules? | tcgmode

Title says it all. Opponent boardwiped and put a bunch of Sephiroth triggers on the stack. They play \[\[Veil of Summer\]\] to give themselves hexproof from black. Sephiroth triggers still go through, and they die anyway. The card says target opponent, so hexproof should've saved them right? Is ...