Unlife Transference

You sacrifice some of your necromantic summon's health to mend another creature’s injuries. One of your undead summons of your choice takes 4d8 necrotic damage, which can’t be reduced in any way, and one creature of your choice that you can see within range regains a number of hit points equal to twice the necrotic damage the summon takes. 

This transference of unlife comes at a cost. Each time a creature is healed in this way, it must mark off one failed death saving throw. The failures are cleared on a long rest.

At Higher Levels. When you cast this spell using a spell slot of 4th level or higher, the damage increases by 1d8 for each slot level above 3rd.