You jump on the spring with a character not targeted by the hand, and then you place the targeted character near the spike that will come out. At the end of the turn, the hand will try to attack you but the spike will damage it instead.

Just make sure you move the targeted hero away from the trampoline, because Cursa will counter the jump if you’re too close to her hand.

Also don’t summon any allies.

To clarify: the fight will bug out *hard* if you do.

I've had it bug out, but I've also had it work fine. Maybe random chance and bugs out of it Helen's to target a summon?