Troll Heartbeat

You ivoke the irregular but powerful heartbeat of a troll within the body of a creature you can see within range. 

The target must make a Constitution saving thow (DC is your spell save DC)

On a failed save the target takes 3d8 necrotic damage, and until the spell ends, it has disadvantage on its next attack roll or saving throw it makes before the end of the next turn. 

On a successful save, the target takes half damage and is not weakened. 

While you maintain concentration, you can use your bonus action at the start of each of your turns to force the creature to take 1d8 necrotic damage as its heart spams unnaturally.

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