Enervation

5th-Level Necromancy
Casting Time: 1 action
Range: 60 feet
Components: VS
Duration: (C) 1 minute

A tendril of inky darkness reaches out from you, touching a creature you can see within range to drain life from it. The target must make a Constitution saving throw. On a failed save, the target takes 4d8 necrotic damage, or half as much damage on a successful one. On subsequent turns, you use your action to force the target to repeat this saving throw again. The spell ends if you use your action to do anything else, if the target is ever outside the spell's range, or if the target has total cover from you.

Whenever the spell deals damage to a target, you regain hit points equal to half the amount of necrotic damage the target takes.

At Higher Levels. When you cast this spell using a spell slot of 6th level or higher, the damage increases by 1d8 for each slot level above 5th.

Source: XGE 155

Changelog

Now is a Con save, and it doesn't end if it succeeds on the initial save.