"At the start of each hero's turn, this card deals that hero character card 2 energy damage."
Argh. I can't even begin to guess how this is supposed to be sorted out. Fortunately, for once, I managed to think of a rules question before it came up in play.
You'd pick one. You have five character cards, 4 of which can receive damage.
I agree that the language used on the T-Ape's card is confusing. This just came up in a game for me and here's how we interpreted it:
The Sentinels have four character cards, but only count as one hero. Remember that they only count as 1H, not 4H, and that the player playing them only gets one play, power, & draw.
A clearer way to for this to have been stated would be if T-Ape said, ""At the start of each hero's turn, this card deals that hero 2 energy damage" with "hero" in this case meaning the team, not each hero target, as The Sentinels only get one turn, not four. The problem comes with T-Ape's use of the term "hero character card" as the player clearly does have four hero character cards (the Vengance rulebook refers to The Sentinels as having four character cards and one setup card).
I'd love if we could get an official answer on whether the T-Ape would target one Sentinel of the player's choice or if it would target all 4 of them, as I keep flip-flopping on how I read this.
Another piece of fuel for this fire: The Scholar's card Proverbs and Axioms says "Each player draws 1 card. Each hero character card may either regain 2HP or deal themselves 3 phychic damage and use a power." This seems to clearly imply that each active member of the Sentinels would get either heal or take damage and use a power, not just one.
And with Sentinels Tactics in play and a Cosmic Weapon in your area you can pull off 5 powers. (Try it with Mainstay taking all their damage at-3 taken, it is fun).
The Ape would hit them all if it said each. Ape works like any card targetting the character card of a deck, the player chooses which Sentinel. This has been confirmed I believe, just don't know where.
That sounds right to me.