As part of your Adven-Tour with Peony, you must investigate the slumbering Regis (the “Terrible Titans”) and awaken them. Each Temple is initially sealed however, and you must solve a puzzle to open the door.
After opening the doors, you’ll need to light up the spots on the ground and then talk to the statue to initiate a battle with the Regi. If you defeat them, you’ll be able to start a new battle by speaking to the statue. If you catch a Regi, you will not be able to battle it again.
How to open the Rock Peak Ruins for Regirock
The Rock Peak Ruins are located in the Giant’s Bed area. The door will give you the hint, “Let the first Pokémon hold a never-changing stone.” Thinking of any common held item in particular?
Walk up to the door with the first Pokémon in your party holding an Everstone. The door will then open.
How to open the Iceberg Ruins for Regice
The Iceberg Ruins are located in the Snowslide Slope area. The path is located to the side of the main slope, as seen in the first picture above. The door will give you the hint, “Walk together with a living crystal of snow.” Hmm… what Pokémon does that remind you of? If you guessed Crygonal, that’s right! They can be caught nearby.
Walk up to the door with a Crygonal in the first slot of your party so that it is following you. The door will then open.
How to open the Iron Ruins for Registeel
The Iron Ruins are located in the Giant’s Bed area. The door will give you the hint, “Let ring the piercing note that will wake the giant of steel.” Know of any way to make a loud whistle?
Press directly down on the left joystick to make a whistling sound (normally used for attracting Pokémon). The door will then open.
How to open the Split-DecisiRuins for Regieleki or Regidrago
The strangely named Split-DecisiRuins are located in the Three Point Pass area, off of the Frigid Sea. The door will give you the hint, “When gather the three giants, the door of destiny shall be opened.”
You need to have Regice, Registeel and Regirock in your party and registered in your Pokédex.
How to encounter Regigigas in The Crown Tundra
To get Regigigas to spawn, you’ll need to visit a special Max Raid Den in the Giant’s Bed area. You can fly to the Snowslide Slope Watt Trader and go directly south. There are four stones that surround the den.
You must have Regirock, Regice, Registeel, Regidrago and Regieleki in your party and interact with the Max Raid Den. A purple beam will appear and you can enter a Max Raid Battle with a level 100 Regigigas.
If you’re still having trouble, check out FancyCharmander’s video below.