Kidney Stone

Kidney Stone causes your cat to take 1 damage and pass a kidney stone at the end of every turn. The kidney stone drops as a terrain object on the battlefield, similar to poop from digestive disorders. The 1 self-damage per turn is a consistent drain on your cat's HP that adds up over long battles, while the kidney stone spawns create terrain that can interact with other mechanics.

Kidney Stone is heritable and can pass from parent to kitten through breeding. It can also be acquired through events or applied with a Disorder Syringe from the Organ Grinder. The guaranteed 1 damage per turn makes this disorder worse than probability-based self-damage disorders since it triggers every single turn without fail. In a 10-turn battle, that is 10 HP lost passively, which can be the difference between surviving and going down.

The kidney stones may interact with Scatological (heal 5 HP when damaging waste) depending on how the game classifies them as terrain objects. If kidney stones count as damageable waste, you could create a healing loop: take 1 damage to spawn a stone, then attack the stone for 5 HP, netting +4 HP per turn. Without such synergy, Kidney Stone is a straightforward negative disorder. High-Constitution cats can absorb the passive damage better, but most builds should replace Kidney Stone with a more beneficial disorder.