|Abomination (left) and Angel (right)|
Abominations are Beastmen whose karma lowered to the point their home planet and race rejected them. They will get new looks, stats and racial skills. Both your look and your attribute bonuses/maluses as an Abomination will depend on the family (sub-race) of your character. Other unique abilities of the original sub-race (e.g. night bonuses for a Shadow Demon) might persist after the transformation too. It's not possible to transform back to Beastman.
Babilis loves Abomination and they can live permanently on the Tartaros.
After completing transformation ritual you will be disconnected and in character selection menu you find your character with changed race. You will be able to finalize appearance of your character but not stats. Your stats will same except for gains and loses caused by transformation.