This should be fairly self explanatory. I was doing some cocaine and CBMs, trying to get a few of the delicious cybernetics I got from a crashed helicopter, when it came time to put in the Night Vision. I failed the installation on a 48% failure chance, and then it suddenly gave me the High Night Vision mutation.
[b][i]“From the bits you came without night vision and without it shall you depart, for what the RNG giveth the RNG taketh away.”
-The book of Angband 4-20
Now that RNG gave you what you wanted expect hulks in every corner. I wouldn’t try mutagen either.