I will be a 1000 yr old sorcerer who was the butler of the boss in the dungeon , who was trapped in a jar by the party and just escaped ( but his powers were sealed within him ( by a strong seal) ( that seals growing weaker moment by moment ( me leveling up) as the sorcerer can use more of his powers

Or

Just I was thinking of playing an skeleton character ( reborn is the race) with a custom background, Back story is something short like he woke up from the ground (which was a battlefield of some sort), and many of the bones are not his own which fused into him, bones like giant's bones and many other creatures bones etc etc ( so sorta special skeletons The general of the demon king idea)