Militant Bajoran Vedek who worked with the Maquis in counterintelligence, but was thrown out for experimenting with mind control as a way to "recruit" agents. Teero was described as an unstable fanatic who would go to any extreme for the Maquis. He called the other rebels traitors for rejecting his ideas and swore he would fight the war on his own if he had to. After the Maquis were eradicated by the Dominion in 2373, Teero apparently did want to continue the struggle, but the only Maquis members left were those stranded in the Delta Quadrant aboard the U.S.S. Voyager. And he had a connection to those comrades by way of a Vulcan spy named Tuvok.
Tuvok met Teero in 2370 while working undercover posing as a Maquis rebel, doing reconnaissance on a colony near the Badlands, where Teero was a Vedek at a Bajoran temple. Teero claimed to be a "student of the mind" who found Tuvok's mind to be disciplined and orderly on the surface, but was repressing roiling emotions and violence. Teero restrained Tuvok in a surgical chair in an underground laboratory, where he attached cortical devices to his head and implanted certain "instructions" in Tuvok's mind to be activated later, then released Tuvok with the memories of his experiment erased.
In 2377 after the U.S.S. Voyager established two-way communications with the Alpha Quadrant, Teero managed to intercept a letter to Tuvok from his son Sek, and embed a subliminal message within the signal. That message was Teero chanting "Pagh'tem'far, B'tanay," meaning "This is a holy time, the Time of Awakening," triggering behavior in Tuvok that led to him attacking members of the crew who were former Maquis, including Chakotay and B'Elanna Torres. Tuvok used his mind-meld capabilities to pass on Teero's instructions to those crewmen, who eventually responded by taking over Voyager and threatening to strand the Starfleet personnel on a Delta Quadrant planet. But ultimately Tuvok was able to counteract Teero's influence, regain control of himself and mind-meld the others back to normal.