Scleroderma

Scleroderma converts your cat's HP into Shield at the start of each battle, stripping all but 1 HP and granting that amount as Shield instead. Shield absorbs damage before HP and does not regenerate naturally, creating a cat that is tanky at the start of fights but progressively more vulnerable as its Shield is stripped away. The 1 remaining HP means any damage that penetrates the Shield is immediately lethal.

Scleroderma 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 HP-to-Shield conversion happens at battle start, so cats with high Constitution benefit most since they convert more HP into Shield. The disorder essentially front-loads all your cat's survivability into a single Shield pool that depletes over the course of the fight.

Strategically, Scleroderma works on high-Constitution cats that can generate a large Shield pool, combined with builds that end fights quickly before the Shield is depleted. It pairs poorly with Touched (cannot heal), which is redundant since you only have 1 HP anyway. Healing effects that restore HP are mostly wasted with Scleroderma since you need Shield recovery instead. The disorder excels in short, intense battles but struggles in prolonged fights where the Shield pool gets whittled down to nothing.