Moziel
This is suggestion for author,if you want to add an oc character in the future can you make him/her with mutant ability like black hole mimicry,or just straight up an sentinent black hole with abilities like absorb(just for regeneration and getting more powerfull,not beelzebub from tensura or absorb from yuuma from touhou),nigh-invulnerable(the character would be black hole meaning any attack would be absorbed and nullified),self-mass and density manipulation and ability to affect timeflow(making it slower or faster but just that) and gravity around user,i tried to find ff with mc who has this power but its like it does not exist,or even similar,like black hole mimicry is so cool you are immortal,invulnerable,you can crush others with you presence,you can slow down time around you to nigh-stop and move at massive ftl speed,and more.
Well even if didn't ,he does now....atleast in this fanfic, I just hope you only give him limited-minor shape-shifting abilities like he can change his skin,hair, and eye color and maybe make other slight changes like if he had same number of fingers and toes as nightcrawler does in canon he can make it so he has same amount of number of digits as the average human by just splitting whatever number of digits he has normally to match the number of digits a human that was born with no deformities. And I like the fact you made so Azazel has to hide his tail in his clothes instead of just being able to shapeshift like mystique does to remove/add, and/or change the form of her limbs.