Twenty Years of Sign-In in the Heavenly Prison: I Became Invincible After Release

Han Mu transmigrates into a fantasy world as a deposed crown prince and is thrown into the imperial prison. With death staring him in the face from the start, he activates a bizarre sign-in System! It even lets him choose a person to sign in with and obtain any of their skills or items! [Host selected the Blazing Sun Old Demon. Sign-in successful. Obtained Blazing Sun Divine Art.] [Host selected the Ice Mystic Empress. Sign-in successful. Obtained Ice Crystal Soft Jade Palm.] Huh... Something strange seems to have slipped in there. Four years later, Han Mu emerges from the imperial prison, stronger than ever. He sets his sights on the throne and ushers in an age of boundless prosperity!