Arm cannon

You fire out the bones of your forearm through your hand, leaving a severe wound that immediately regrows and heals. Make a ranged spell attack. On a hit, the target takes 4d8 piercing damage and must succeed on a Strength saving throw or be pushed back 15 feet. If pushed into an obstacle, the target is impaled on it, and is restrained by the bone until the start of its next turn. Creatures that are Large or larger have advantage on this saving throw.