Spend enough time beside another mutant on Krakoa and you start to change.

Symbiosis is a relationship‑progression system. It represents the way repeated social contact with another mutant makes your character adapt to them: picking up habits, instincts, resistances, and eventually shared techniques that only exist because of the bond.

It deliberately separates what the relationship is from how strong the bond is. You name your own relationships: Friend, Rival, Mentor, Nemesis, Drinking Buddy, Crush; and the label carries no rules weight at all. The Relationship Level does.

Plasticity is the biological metaphor at the heart of the system. Repeated interaction creates the capacity for adaptation: the more your character engages, the more they can be changed by the people around them. Your relationships don't just record who you know. They physically and behaviourally change who your character is.

You earn Plasticity by engaging with other players: making a First Impression, turning in your roleplay bounties with other characters, and submitting social scenes, all subject to a weekly cap.

Each bond has a Level from I to V.

There is a one‑level difference limit. Neither character can be more than one Level ahead of the other: if you are Level III with Wolverine, Wolverine can be Level II, III, or IV with you, but not I or V. This makes Symbiosis inherently reciprocal without forcing the two characters to feel exactly the same way about one another.

1. IHabit. The other mutant starts rubbing off on you. On reaching Level I you choose one of three Habit Perks tied to their mutant nature: small always‑on adaptations you develop just from being around them. These aren't generic friendship bonuses: their specific nature decides what you can pick up.
2. IIAdaptation. The bond has moved past habit. Your character has actively adapted. The benefits get stronger and more specialised, and the relationship can begin developing its first Symbiosis Technique: the start of the two of you being able to merge your powers to great results.
3. IIISynergy. Genuine mechanical synergy. Your abilities, instincts, or behaviours start producing effects neither character has alone: You gain access to Synergy Perks that activate whenever you are together.
4. IVInterdependence. TBD
5. VSymbiosis. The culmination. The pair are adapted to one another deeply enough to act almost like a single social organism, capable of developing their Symbiosis Technique at will.

When you establish Level I Symbiosis with a character you pick one of the three perks below, drawn from their Mutant Class. In play: +symbiosis/bond <name> to establish the bond, then +symbiosis/perk <name>=<perk> to choose.