Animated movie with monster and "chosen ones" kids


Quite literally have been stuck on this for nearly six years now.

6 kids, 3 on good side and 3 on bad. Two boys and one girl for each side. They were all younger than like 13 or 14. The good kids were supposedly the chosen ones and were found by a monster who said that they had to come save his world, so they went into some backroom of a building and went through a portal on the wall to go save this world. Meanwhile, on the bad kids side were once again, two boys and one girl. The girl was younger than the boys and had dark green hairs and eyes and wore dark clothes. She was the younger sister (possibly adopted) to one of the other bad kids. They also entered the other world to try and stop the good kids.

A battle took place at pyramid between the two sides where I think the kids evolved into these monsters or something to fight. At the end of the movie, the good kids finished their quest and this bright light shined on them, but then the bad kids started to raise up and their eyes started to glow. At that moment, the characters found out that it was the bad kids who were really the chosen ones and not the good kids.

Western animation style movie.