The Tri is one of the non-playable characters in Lego Dimensions and a minor character in Lego Dimensions 2: The Rise of Enoch.
During the prologue, Lord Vortech captures three sidekick characters from different worlds using rifts, he takes the Foundation Elements each of them were carrying, added them to his collection and trapped the three in his lair. When Batman, Gandalf and Wyldstyle arrive at Foundation Prime to rescue them, Vortech combines the three heroes using Robin, Frodo, and MetalBeard's heads and bodies forming the Tri which he commands to collide the dimensions, beginning with The LEGO Movie World.
The Tri appears on The Octan Tower and attacks the trio knocking them back and then it activates a Keystone. Just before the trio can reach the Tri it pulls them through a rift into the Lord of the Rings world. After navigating through this world the Tri once again pulls them through a rift this time taking them to Gotham City.
At the end of the chase the trio must fight against The Tri in Gotham while two dimensions merge together in the background. During the fight the trio break into the Tri's body and rescue one of the captured sidekicks, this happens three times and once all three are rescued they attempt to escape. Batman discovers a piece of Vortech inside and throws a batarang at it causing it to implode destroying the Tri and almost the heroes who narrowly escape through a rift.
In Lego Dimensions 2: The Rise of Enoch, titular main antagonist Grand Emperor Enoch along with Karnia are given a tour by Foundation Crime. The leader of the cult, Bellosh, leads them to the trophy room and shows them all of the trophies they won and/or stole. Enoch sees a statue of The Tri, knowing that Bellosh has been fascinated with it and it's powers before seeing a vision of Lord Vortech and coming up with a new plan to recreate the Multiverse by destroying it first. By the time Enoch and his allies left, the statue was nowhere to be seen again.
However, in Fate of the Multiverse, Enoch used the Equation Keystone to clone the statue while using his powers to bring it to life. He then uses the Scale Keystone (similar to how Lord Vortech uses it) to make it grow the same size as it was in The End is Tri.