The Tavern

Is there ANY way to control which way demonspawn mutations go?

play seeded games

the combination of seed and game version determines the mutations. you can copy the seed from some-one else's character dump or from your own games.

And once the seed has been generated there's no way to change it?
I wanted to make a Demonspawn enchanter with the mutation that paralyses adjacent enemies to see how far i could get him, but it's just too random.

Indeed, based on my experiments the seed fixes the mutations you'll get