An easy to read image of mutations found.
Mutations
I have found only a few notes and threads with info on the Mutations available and although only found Corrupted and Mystic so far, I have compiled info from other users into a easier to read sheet.

I have read that Hollow and Spectral are the rarest to come across. It also would appear that the more often you make a specific monster, the chance of it being a mutation increases.
I did make the assumption that the mutated stat increases or decreases by approximately 25% based on limited level 1 beasts. Also this is my 1st guide I’ve posted. Generally I just keep all my data on a spreadsheet, but hopefully someone else can make some use of this as well.
Edited: Fixed Tiny strength negative value and cleaned up image a bit.