Walkthrough
As you complete The Terrible Titans... Lurking Locked Away Adventure, you will have to go through a number of various areas across the Crown Tundra in search of the Regi Legendary Pokemon Group. One of these areas is the Split-DecisiRuins found within Three-Point Pass, which is where another of the Regi Legends can be found. In order to open the door to the ruins, you must have Regice, Registeel and Regirock in your party.
Unfortunately, players will only be able to obtain one of the two newest Regi Legends depending on the pattern they create with the light up tiles on the ground. If you light all the tiles on the left side, all the tiles on the right side and the second highest tile in the middle row, you will go into battle against Regieleki when you click on the statue. If you light the top two tiles on the left side, the top two tiles on the right side and the top tile and two bottom tiles in the middle row, you will go into battle against Regidrago when you click on the statue.
Interactable Pokemon
Regieleki: Level 70
Regidrago: Level 70