Bowser

Damage Immunity. Immune to all damage types except bludgeoning and flame damage.

Axehands. Bowser throws two axes at the target. Roll to hit (D20+3) for each axe. Axes deal 1d4 damage on hit. 

Body Slam. Target must make a Dex save.
On a 0-5, target takes 1d4 bludgeoning damage and is knocked prone.
On a 6-11, target takes 1d4 bludgeoning damage.
On a 12+, the attack misses.

Shell Spin. Bowser falls prone and pulls his limbs into his shell, leaving only his spikes exposed. The shell spins rapidly and moves 30 feet in any one direction. Targets in the shell's path must make a Dex save of DC 11 or take 1d8 piercing damage. Bowser is prone and is stunned until the start of his next turn.

Jump. Bowser jumps into the air, granting him +1 to AC until his next turn. Cannot be used with Shell Spin.