It's a tall humanoid white monster-like android with red eyes and black stripes on it's head.
It shows absolutely no personality, it's mute and just wreaks havoc.
The monster can shape-shift it's body into anything it touches like concrete, water, metal, oil, and fire. The four remaining Teen Titans fought the monster, but were no match without Beast Boy's help (because Beast Boy saw a girl who he thought was Terra. Beast Boy then let the girl go and ran off to help his friends fight the monster. The monster's defeat was never shown (due to the fact that the TV series was cancelled). Therefore the monster's fate remains unknown.
However in 2011, Greg Cipes, the voice of Beast Boy on the show, had stated that work on a new season was underway and that a live action Teen Titans film was planned for release at the end of 2012. In 2012, Derrick Wyatt (animation designer of the series) stated the next arc would feature the Titans setting up international Towers, and battling the monster from the season 5 finale. But as of 2020 there has been no known progress on the series at all and it's unknown if there ever will be.
The White Monster is the final antagonist in the series who the Teen Titans face.