Immortal

Immortal reduces all damage your cat takes to 1, regardless of how much damage the attack would normally deal. A boss attack that would deal 20 damage? Your cat takes 1. A multi-hit combo that would normally be lethal? Each hit deals only 1. This is one of the most powerful defensive effects in the entire game, making your cat virtually indestructible against high-damage attacks while remaining vulnerable only to sustained chip damage from many small hits.

Immortal 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 damage reduction applies to every individual hit, so multi-hit attacks deal 1 damage per hit rather than 1 total. Status effect damage (Poison, Burn, Bleed) likely also gets reduced to 1 per tick, making Immortal cats resistant to damage-over-time effects as well.

Immortal is a top-tier disorder alongside Brain Dead, The Shining, and Nudist. It has no downside and provides massive survivability. Pairing Immortal with Brain Dead creates an unkillable cat that also levels up faster. With The Hunger (lifesteal on basics), the 1 damage per hit means any heal from attacking keeps the cat at full health. Immortal is especially valuable against bosses with devastating single hits that would normally one-shot cats. The only threat to an Immortal cat is being swarmed by many attackers dealing 1 damage each, slowly whittling it down through volume.