Dead Mans Swords

You drop a broken sword into a small portal. Above your target, the other end of the opens and five broken swords fall threw. On a hit, the target takes 1d10 necrotic damage, and can't regain those hit points. If you hit an undead target, it must succeed in a wisdom saving throw or fall under your control for 1 hour. If you hit an alive target, it must succeed in a dexterity saving throw or take 1d10 for a bonus action.

This spell's damage increases by 1d10 when you reach 7th level (2d10), 13th level (3d10), and 20th level (4d10).