Normal- 16/17 years, he hasn't been arrested(or maybe he has?) and is therefore loose and things are bound to get chaotic. He's not above lying to everyone and treats people as pawns in some cruel game. He can be brutal, revelling in others' weaknesses and fears.
Chrome- Nagi Rokudo was horrifically injured in an accident and 17 year old Mukuro contacted her mentally from within the prison where he is being held. She accepted his help and he uses her as a bridge between his cell and reality, possessing her during fights through the trident she carries.
Mukurou(Mukurowl)- 26 year old Mukuro fights for the Vongola until he is brutally defeated. His last effort is self-sabotage- he cuts the wing of his Box Weapon, a snowy owl. Glo Xinia takes the box weapon and uses it to try and strike down Chrome; Mukuro possesses the owl with what little strength he holds and the combined power of Chrome and his power blows the man away easily. The owl(Fukurou) is dubbed "Mukurou"(Mukurowl) as a pun on "Mukuro's Owl"(Fukurou no Mukuro)
TYL- 27 year old Mukuro has escaped Vendice with the help of allies of great power. While his body is physically weak, his mind is greater than ever before. He seems less deceitful toward his allies but more likely to take a hit to save Chrome, though he states it's because he needs her body.
Current- At age 19, he is freed after the Vendice Arcabaleno tries to kill him and Chrome is possessed by Daemon Spade in order to fight. And because apparently the Vendice hating him and his offer to help overthrows about 50 murders and three counts of kidnapping.