Mutation spell effect

Hello all, i am currently looking for a means to produce a spell that would in essence cause one to gain a random mutation.

I am hard at work on a super power mod and this effect would go along with the evolution power, which for a suitably high fatigue cost would cause one to gain a random mutation.

Only issue is i can’t figure out how to cause the mutation effect to happen when the ability is used. Help would be appreciated!