Drain Soul

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

A wispy blue cloud of life is drawn from the target, which you consume to recharge your magic.
The target must make a Charisma saving throw. On a failed save, the target takes 3d12 shadow 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 the target, you regain 1 mana for every 5 shadow damage damage the target takes.
This spell has no effect on undead, constructs, and creatures with no soul (though the GM may allow you to use it on spiritual undead or constructs that have been empowered by soul energy.)
At Higher Levels. When you cast this spell using a spell slot of 6th or higher, the damage increases by 1d12 for each slot level above 5th.

Source: Homebrew