Teero was a fanatic, determined to fight the Cardassians and even experimented with mind control in an attempt to get new agents. He attempted to join the Maquis in their fight against Cardassians, however, he was dismissed since his methods were too extreme.
In 2371, he captured Lieutenant Tuvok and implanted suppressed memory commands into him at a colony near the Badlands. These commands would activate when Tuvok heard the Bajoran chant "Pagh'tem'far, B'tanay".
In 2377, a few years after the Dominion had crushed the Maquis resistance in the Alpha Quadrant, Teero found out that the USS Voyager, whose crew was one-quarter Maquis, was still active in the Delta Quadrant, and that Tuvok was still alive. With the Maquis having been decimated by the Dominion, Teero saw an opportunity to revive it.
He embedded a subliminal message containing the Bajoran chant into a letter to Tuvok from his son Sek. His instructions were for Tuvok to use mind melds to implant commands into the other Maquis members of the crew to take over the ship, abandon the Starfleet crew, and travel back to the Alpha Quadrant as fast as possible with the powerful ship at his command. They were subsequently activated by repeating the Bajoran chant.
Voyager was almost taken by Teero Anaydis (albeit by proxy) and his new 'recruits'; however, Tuvok managed to reclaim control of his mind and used the mind meld technique to undo Teero's control of the other Maquis crew members, stopping the mutiny. Teero later learned that his technique succeeded, but that the takeover failed. (VOY: "Repression")