Regirock
Gender: No Gender, Referred as ♂
Creation Name: Regirock/Codename: Adam
Personality: Robot-like, Emotionless, Merciless…
Favorite color(s): Has no favorite…
Time of Creation: approx. 4500 years ago?
Time of Death: (INVALID)
Time of Rebirth: (INVALID)
Form before Rebirth: (INVALID)
Favorite Animal(s): (INVALID)
Parentage: Regigigas (Creator/Builder)

Regice
Gender: No Gender, Referred as ♂
Creation Name: Regice/Codename; Borealis
Personality: Robot-like, Emotionless, Merciless…
Favorite color(s): Has no favorite…
Time of Creation: approx. 4500 years ago?
Time of Death: (INVALID)
Time of Rebirth: (INVALID)
Form before Rebirth: (INVALID)
Favorite Animal(s): (INVALID)
Parentage: Regigigas (Creator/Builder)

Registeel
Gender: No Gender, Referred as ♂
Creation Name: Registeel/Codename: Kin
Personality: Robot-like, Emotionless, Merciless…
Favorite color(s): Has no favorite…
Time of Creation: approx. 4500 years ago?
Time of Death: (INVALID)
Time of Rebirth: (INVALID)
Form before Rebirth: (INVALID)
Favorite Animal(s): (INVALID)
Parentage: Regigigas (Creator/Builder)

Biography;
Regirock, Regice, and Registeel are very unique among Legendary Pokémon, in that they are machines, robots forged from raw materials by the Legendary Regigigas. Though they are made through a way that even advanced civilizations would deem magical, the three golems are actually highly advanced robots, lacking gears, springs, and other mechanical whatsits, effectively making them malfunction proof. Even when they are considered the perfect machines, Regigigas deemed all three a failure, as they lacked the human soul, leaving their moral compasses non-existent, and being too much like mindless machines. Their programing is also deemed a failure by Regigigas, as where he aimed to make them more alive, they instead behaved much like how people think a stereotypical robot would behave. Even when Regigigas thought of his creations as failures, he does admit that their combat efficiency far exceeded his expectations, but was disappointed that all three were downright brutal, because they lacked moral limits.

Regirock was made from the same rocks where the ancient city of Petra would stand in the present, since its temple sat on holy grounds, Regirock can be considered a holy weapon, something demons fear above all else. Regice was made from an ancient glacier from the Ice Age that ironically sat upon holy ground, and like Regirock, Regice can be considered a holy weapon, using ‘his’ power of ice to freeze and shatter demons. Registeel is a little different, in that he is made from a holy metal ore forged by Heatran, and the same metal ore is believed to be able to harm demons, and the fire used to construct his frame burned hotter than the surface of the sun. All three were created by Regigigas as tests to see if golems can be used as weapons against the forces of Hell, and though Regirock, Regice, and Registeel were a little too successful, and somehow gave the early humans the desire to create protectors like them, thus beginning the many legends of golems in the Old World. Due to a mishap by Celebi, the Legendary Golems had inspired ancient advanced civilizations to create their inanimate robots to perform duties as protectors as well, believed to be the start of the Pokémon, Golett and Golurk.

Some of the people began to fear Regigigas’ creations, and an unknown crusade was formed to either destroy or seal away the golems. Because of self-defense protocols and an un-programmed code, the Legendary Golems thought the humans turned to side with the demons, and mercilessly destroyed the armies used against them. This prompted both Regigigas and God to seal them away, and because the humans were angry at Regigigas himself for creating the monsters they called them, he accepted the burden and punishment to be sealed away by the humans to a faraway land in the west.

Regigigas longs to rebuild Regirock, Regice, and Registeel in a less hostile and more intelligent AI programming, but feels he can’t do it so long as the original Regirock, Regice, and Registeel are still functioning and still are roaming the planet.
Each of the Legendary Golems have access to many ELECTRIC-type moves and many different protocols imputed in their AI, including a fail-safe combat protocol that is the reason Regigigas considers all three a failure, dubbed the “Terminator Mode”. While in “Terminator Mode”, Regirock, Regice, and Registeel are at their most merciless, becoming unstoppable fighting, ergo killing machines that terminate their foes with ruthlessly efficiency, not even allowing their foe to catch his/her breath, and ignoring their pleas for mercy. Their AI is remarkably similar, if not more advanced than modern-day AI, and this makes them able to connect to many wireless devices. Even under the threat of viruses or hackers, their AI programming is so ancient and needlessly complex that the three Legendary Golems are virtually hack-proof and virus-proof, whether that is a good or bad thing is up for debate…

4877378 A very interesting and dark headcanon.