Suppress Regeneration

1st-level transmutation
Casting time: 1 action
Range: 30 feet
Target: a creature you can see within range
Components: V, S, M (skin from a troll or other regenerating creature)
Duration: Concentration, up to 1 minute
Classes: Sorcerer, Warlock, Wizard
Subclasses:

You temporarily remove the ability to regenerate from a creature you can see within range. The target must make a Constitution saving throw. On a failed save, the target can’t regain hit points from the Regeneration trait or similar spell or trait for the duration. The target can receive magical healing or regain hit points from other traits, spells, or actions, as normal. At the end of each of its turns, the target can make another Constitution saving throw. On a success, the spell ends on the target.

At Higher Levels. When you cast this spell using a spell slot of 2nd level or higher, you can target one additional creature for each slot level above 1st. The creatures must be within 30 feet of each other when you target them.