Angelheart Protector

The trigger reads "target creature you control," and that self-legal clause is what separates this from a fragile support piece. Point the indestructibility at another attacker and combat math bends your way, or name a keeper before you fire off your own board wipe and rebuild from a clear field with the best thing you had intact. But there is no requirement to have that keeper: on an empty board it simply targets itself, arriving as an indestructible 3/2 rather than an inert body. The constraint that shapes everything is timing. It triggers when the creature enters and the immunity lapses when the turn ends, so this is a proactive tool and never a reactive one. You cannot hold it up over a removal spell on the stack, and it answers nothing an opponent does on their own turn. The window it buys is tied to when the creature enters, which typically means the protection has expired by the time an opponent can act: no permanent ward, no repeatable engine, and no easy way to save a creature on a turn that isn't yours unless you can flicker it in at instant speed. What it protects against, then, is your own aggression and your own board wipes, plus anything the opponent commits during your turn (a blocker's combat damage, an instant-speed removal spell cast in response to your attack). The upside scales with the rest of your board, but even at floor it is a body that clears your own sweeper without a second thought.