The Abyss is an interesting card. At the beginning of each player’s upkeep, it makes that player choose a target nonartifact creature he or she controls to destroy. Note the word “target” there, because it’s pretty important. It means The Abyss’s trigger can’t target a creature with shroud or protection from black, obviously.
What about hexproof? What about the ultimate hexproof found on True-Name Nemesis? Well, that’s where the controller of the ability becomes important. It seems natural to think that if you’re choosing the target, you’re the controller. However, the controller of a triggered ability is always the controller of the source of that ability when it triggered. So no matter whose turn it is, whoever controls The Abyss also controls the ability, even if that controller isn’t choosing the target.
So if it’s my Abyss and my hexproof creature, the answer is intuitive, and I can target it with the ability (or must target it if it’s my only creature).
If it’s my opponent’s Abyss and my hexproof creature or my True-Name Nemesis with protection from the Abyss’s controller, I can’t choose to target my creature since it’s not a legal target for that ability I don’t control. My creature gets to happily ignore the Abyss forever. Of course, if I have any other creatures that could be legally targeted, I’ll have to choose one of those instead… I can’t just say, “I choose to target my Nemesis, but I can’t, so I’m totally off the hook!”
Today’s Rules Tip written by Josh Stansfield