Tardigan was a citizen of Las Vegas and the only survivor of the bio-bomb epidemic. He was a water bear, and therefore capable of surviving intense heat, cold, and pressure. His natural armor also made him virtually invulnerable.
Before the bio-bomb went off, Tardigan worked as a metalworker in a factory.
When the bio-bomb wiped out the population of Las Vegas, Tardigan survived due to his abilities, however, seeing everyone he ever knew vaporized drove him insane. He became obsessed with dying, and filled the city with death traps designed to kill him; however his natural abilities kept him alive. He also killed anyone who entered Las Vegas, giving them the gift he could never have himself.
He encountered Kagetora and Vic in an abandoned supermarket, and almost prevented Kegatora from rescuing Neku from one of Tardigan's traps. While originally Tardigan seemed friendly, offering to let the team stay at his factory, he then kidnapped Snow during the night and activated every death trap in the city. He later fought Neku and would have killed him had the S.S. Hawkeye not dropped explosives on him. Immediately after that, Kagetora sacrificed himself to stop Tardigan from killing everyone else.
The next day, Tardigan beseiged the survivors (along with their new Pelvanida allies]]) in Crimson Base. He killed Hawkeye and his actions led to the death of Ken and the reactivation of Snow's and Neku's powers. The two fought Tardigan in an epic elemental battle, where Neku finally killed his foe. Tardigan's last words, whispered into Neku's ear, were "Thank you." (Ground One)