Gamma moth

A is a type of insect that generally appears deep underground. Its unique attack can cause creatures to gain random mutations (usually defects) or mutation points.

Mutating Gaze
A creature struck by a mutating gaze attack, whether or not the attack penetrates their armor, must succeed at a Toughness save with a target of 20, or else gain the mutating effect. The effect is not applied if the creature is already mutating from a mutating gaze.

Mutating gazes are EMP-sensitive. They will be unable to fire if EMP'd.

Mutating Effect
Mutating has an incubation period of 100 game turns. After the halfway point of this duration, the mutating creature's mutation buys are permuted every turn with the message "you feel increasingly unstable." At the end, one of the following effects happens:

The mutation granted must be one that the creature is eligible for in the first place, so, e.g., Chimeras cannot gain mental mutations (including defects), and  Espers 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).

Tips

 * The best way to avoid being mutated by a gamma moth is to have high Toughness, high DV, or preferably both.
 * It's possible to gain positive mutations from a gamma moth, but it's less common than gaining defects.
 * Because the Mutating effect rerolls your genome repeatedly immediately before its effects are determined, it is possible to use Precognition to reroll the effects of a Gamma Moth's mutation; however, doing so safely is extremely difficult.
 * Mutating lasts 100 turns, so to be able to revert back to before you started mutating and reroll as many times as you want you will need a Precognition of at level 23, plus a method (like Teleportation) to reliably escape after ending your vision without being hit again.
 * If you don't mind a more risky strategy, you can actually reroll a Gamma Moth effect with any level of Precognition, since your genome is shuffled every turn near the end; however, this will only allow you to reroll your mutation once per hit, since after that your Precognition will be on cooldown - without a precognition capable of reverting you to before you were struck, you still be mutating and will be stuck with your second result. Mass Mind allows a third reroll, and with exceptionally high Willpower you may even be able to reroll one or two more times after that by letting it cool down.  Provided you have at least decent willpower,  can buy you a few more rerolls by decreasing the cooldown on Precognition (and Mass Mind if you have it.)
 * When using weaker levels of Precognition to reroll the result, it is extremely important that you time your activation so that it covers the actual moment when the mutating effect ends and you see your result - if you activate Precognition too soon, it will wear off before that and you'll lose your chance to reroll. When you start getting messages that say that "you feel increasingly unstable", you are halfway through the 100-turn duration.
 * True Kin can use to reroll repeatedly, provided they use them with proper timing.  Remember, you will need one injector for each reroll that proves necessary, so bring as many as you can.  Having an intravenous port helps; in fact, implanting three of them at once will extend the duration of sphynx salt to over 100 turns, making it possible to use the safe strategy as above.
 * Another option to exploit Gamma Moths is simply to accept gaining every single defect; once you have them all, there's no longer any further risk to being mutated by a Gamma Moth. In exchange, you can eventually use gamma moths to learn every single positive mutation and raise them all to level 10. While accepting every defect in the game may seem crippling, the advantages of every positive mutation more than outweigh them (with the possible exception of Evil Twin, since your twin will be likewise freakishly powerful and will have to be handled carefully.)  Note that unless you are a Chimera, doing this will raise your Psychic Glimmer extremely high (and the fact that you are accepting Irritable Genome means you won't be able to avoid this.)  If you intend to do this, you may want to learn Psychometry, Horns, and Photosynthetic Skin in advance, which will let you avoid Albino, Carnivorous, Dystechnia, and Psionic Migraines.