As a FF fan this came to mind as it's one of the most annoying end-game ailments; the Zombie status ailment. This would be pretty cool and useful to have in my Death's utility, preventing bosses from healing a good portion of their health and instead deal damage to them.
I think the spell could be something like this, a manipulation trap, so that the effect only affects one target at a time as well is a lot easier to implement than an outgoing heal. For the pip cost, I think it would be between 2-4 pips.