Metabolic, Negative, Removable
Infobox data from game version 188.8.131.52
In the process of mutating.
You start to feel unstable.
The mutating effect is caused by a 's . See that article for more details, or read the following excerpt:
Mutating has an incubation period of 100 game turns. After the halfway point of this duration, the mutating creature's mutation buys and results are permuted every turn with the message "you feel increasingly unstable." At the end, one of the following effects happens:
|80%||The creature gains a random defect.|
|10%||The creature gains a random positive mutation.|
|10%||The creature gains 1d41-4 (Avg: 2.5) mutation points.|
The mutation granted must be one that the creature is eligible for in the first place, so, e.g., cannot gain mental mutations (including defects), and cannot gain physical ones. True Kin, on the other hand, can gain any type of mutation, and can gain mutation points to level them up.
It's possible to have multiple simultaneous defects from gamma moths, regardless of whether the "Disable defect mutation limit" option is set (that option applies only to character generation).