Ninja Gaiden

By releasing a complex seal stored within your body, your cells divide at accelerated rates, healing all wounds at a terrifying pace. You glow with a diamond-shaped seal as the technique consumes your stored chakra. Instantly heal 5d10 + 30 HP, and for the next 3 turns, regenerate 15 HP at the start of each round. You cannot be killed unless reduced to 0 and damaged again in the same round. Usable once per long rest, requiring DM approval for stored chakra or item trigger.