Demon Within

One humanoid of your choice within range becomes a gateway for a demon to enter the plane of existence you are on. You choose the demon’s type from among those of challenge rating of 4 or lower. The target must make a Wisdom saving throw. On a success, the gateway fails to open, and the spell has no effect. On a failed save, the target takes 4d6 force damage from the demon’s attempt to claw its way through the gate. For the spell’s duration, you can use a bonus action to further agitate the demon, dealing an additional 2d6 force damage to the target each time. If the target drops to 0 hit points while affected by this spell, the demon tears through the body and appears in the same space as its now incapacitated or dead victim. You do not control this demon; it is free to either attack or leave the area as it chooses. The demon disappears after 24 hours or when it drops to 0 hit points.