Some TMNT stuff really isn't for little kids.
Zenter is the king of Planet Neutrino, husband of Queen Gizzla and the father of Princess Trib. In the story arc Krang War, he was abducted by General Krang's forces and held hostage, but was later freed by the Turtles and their Neutrino allies.
Zenter later met the Turtles again when the Trial of Krang became a priority, and the four mutants offered their help in getting important witnesses to Krang's past atrocities. When Judge Gorath was murdered, Zenter took the position of judge himself, doing his best to remain fair.
During this time, the Malignoid swarm was approaching the Neutrino planet, and Zenter had promised the Triceratons a new homeworld of their own if they defended his world. He was guilt-ridden after Krang pointed out how he was hypocritically using the Triceratons for his own ends, and thus (in Krang's view) was in no position of moral superiority. In the interest of fairness, Zenter contacted Ma'riell to arrange proper imprisonment for Krang, although this ultimately did not come to pass as Krang was attacked and eaten by Leatherhead before transit.
After the Turtles' departure, Zenter contacted the Triceratons and told them that their true home was Earth. Incorrectly assuming that the Turtles' own kindness and nobility was indicative of all people on Earth, he opened a portal to permit the Triceratons to return to their ancestral world.