It is not known to evolve into or from any other Pokémon.
It comes to life only when Regirock, Regice, and Registeel are gathered. Therefore, it requires the three to be in the player's party to awaken it within the Snowpoint Temple, Twist Mountain, or Island Cave, where it sleeps. In the former two locations, it will still be present if those Pokémon are absent, but it does not awaken and only seems to be a statue to the player.
It is the trio master of Hoenn's Legendary golems.
Regigigas appeared in Giratina and the Sky Warrior. In the movie, it lives in a temple in the mountains of Gracidea. It had been asleep for centuries, for so long that moss began to grow on its body. However, when Zero entered the Reverse World and began shattering pillars of ice within it, the glacier in front of Regigigas' temple suffered catastrophic explosions and began moving. This disturbed the great titan's slumber, rousing it into action. When Dawn's Buneary and Swinub failed to stop the glacier with the help of a large group of wild Pokémon, Regigigas appeared in the command of a herd of dozens of Mamoswine and together, they began pushing on the glacier to hold it back. Regigigas returned to its temple at the end of the movie, where it is seen using Hyper Beam on Team Rocket during the credits.
Another Regigigas appeared in Pillars of Friendship! at the Snowpoint Temple. J wanted to steal it so it was rudely awakened by her. It went on a rampage after, using Hyper Beam on practically anything. It even used Confuse Ray to control Pyramid King Brandon's set of Legendary golems to help it. At the end of the episode, it healed Brandon and his golems using Hidden Power to restore them from their petrification. It was then taken back to the temple to return to its slumber.
A Regigigas appeared in the second XY series movie, Hoopa and the Clash of Ages. One hundred years prior to the events of the movie, it was summoned by Hoopa alongside a Reshiram and Zekrom. The three fought Hoopa in Dahara City but were easily defeated and sent back through portals to their original homes; in Regigigas's case, this was a snowy mountain range.
A Regigigas appeared as part of Meowth's boss fantasy in Dealing With a Fierce Double Ditto Drama!, alongside Giratina.
A Regigigas appeared in the opening scenes of Zoroark: Master of Illusions.
Entry: Regigigas, the Colossal Pokémon. According to legend, Regigigas has towed continents using ropes.