A broad term that describes the physical affects of repeated Sensecraft absorption on the body. Only contact with a Terminus contributes; the actual use of Sensecraft and having it used on you do not.

If unchecked, the process sees the Crafter gradually transform into a Craftborn, specifically the type associated with the chosen Craft. Further absorption will trigger increasingly monstrous transformations, which may also become permanent. (See the various Craftborn articles for more details on the exact nature of these transformations.)

One's level of mutation and Sensecraft capability go hand in hand. It is not possible to achieve the strongest feats a Craft has to offer without taking on physical changes, especially permanent ones. Official organizations categorize this progression using the "SEM" scale (short for SEnsecraft Mutation), the levels of which are as follows:

• SEM 0: No Sensecraft ability, nor permanent mutations.


• SEM 1: Some Sensecraft ability. Capable of strengthening or weakening a sense. Other targets may only be affected given physical contact. No mutations.


• SEM 2: Some mutations present. These changes are temporary and will recede if the Crafter uses all their remaining energy, then ceases absorption for an extended period of time. Those at this level often have greater proficiency in their Craft, and are considered at high risk for reaching further levels. Sometimes called "mutts."


• SEM 3: Permanent transformation into a Craftborn. Additionally capable of triggering hallucinations in the chosen sense as long as their Craft is replenished often enough. Switchsickness is now unavoidable if a different Craft type is absorbed, though the Crafter may eventually transform into a Craftborn of the new type given persistence. Those who bear children will always give birth to additional Craftborn; a human mother and Craftborn father have a roughly 50/50 chance of it.


• SEM 4: Further, increasingly grotesque mutations. May also show changes in personality, especially increased impulsiveness and aggression. Now capable of altering the sense at a distance, with more heavily mutated Crafters able to do so from farther away. These changes are temporary like those of SEM 2, but the ability to Craft at a distance will fade away with them, and the Crafter may only revert as far as SEM 3, even if they allow their Sensecraft to run out entirely. Reaching this level is illegal by default in most countries. If one's job depends on it, they may secure a license, but it must be clearly displayed at all times when in public. Sometimes called "muties," though the term can be used derogatorily towards people with any level of mutation.


• SEM 5: Permanent mutation at the highest level. Those who reach this stage become twisted monsters incapable of living among society. Few Crafters live long at this point, whether due to giving themselves up voluntarily, or being executed for the safety of the public. Usually called "full mutants." Soon after reaching this stage, most mutants use up all their remaining Craft in a massive burst. If left to their own devices, they will seek out the Terminus to restock, but by then they've typically been either eliminated or captured.

How much contact is needed to see any changes varies between individuals, but most estimates cite three to five Terminus visits with minimal waiting time in-between to progress to the next level.