"Todd" first appears in the third season episode "Common Ground", and is a recurring character in the fourth season, where his "name" is given. He is played by Christopher Heyerdahl and distinguished by a starburst-shaped tattoo centered around his left eye. His personality is rather unusual for a Wraith, as he possesses a sense of humor and a certain degree of honor. He is first encountered as a prisoner of Acastus Kolya, who uses him to torture Sheppard by feeding on him repeatedly. He and Sheppard come to an understanding and help each other escape, during which Todd drains Sheppard's life to defeat the Genii and then returns it, an act Wraith perform only for their most devout worshippers and their brothers.
Todd returns in "The Seer", to forge an alliance with Atlantis against the Asurans, informing Atlantis of their new strategy of wiping out every human in the galaxy to deprive the Wraith of their food supply. He requests Rodney McKay's cooperation in modifying their computer virus to shut off the Asurans' attack command, as it was McKay's tampering with the Asuran base code that made it ineffective in the first place. Todd is stranded on Atlantis after his hive ship is destroyed by another suspicious hive, and remains in captivity working with McKay until the episode "Be All My Sins Remember'd". During this time he hacks McKay's computer and obtains data on the Intergalactic Gate Bridge, allowing the Wraith to invade the SGC. Todd however later claims that the data was stolen from him.
In the episode "Be All My Sins Remember'd", Todd convinces seven hive-ships to join the Atlanteans in battling the Asurans, gaining his freedom in the process. During the battle he commands one of the hive-ships, surreptitiously launching a mission to steal ZPMs from the Asuran city. The ZPMs are stolen from him in "Spoils of War" by another hive, to use in powering a cloning facility. Todd is due to be fed upon, but is rescued by the Atlantis team and helps them destroy the facility. He escapes in a dart separately from Sheppard's team. The Atlanteans encounter Todd again in "The Kindred", while investigating a Wraith facility where many have been killed by the Hoffan drug. Todd informs them that all the Wraith factions have been affected, and asks for information on the drug so that he can develop an antidote. The Atlantis Expedition trades him the data in exchange for intelligence on where Michael is keeping Teyla. In the alternate future of "The Last Man", Todd dies fighting alongside Ronon Dex to destroy one of Michael's research facilities, the two sacrificing themselves to allow Ronon's strike force to escape before setting off their explosives.
In "The Queen", the Atlantis team negotiates with Todd to distribute a gene therapy among the Wraith that would remove their need to feed on humans, as Michael had done to himself. Todd convinces Teyla to act as his hive's queen to propose the plan to the leader of his alliance, but instead installs her as the new leader. After Teyla's position as the leader is made secure, Todd is left to lead in her place, effectively giving him control of all the Wraith in the alliance, which Sheppard suspects he might have planned all along. He opts against proposing that the Wraith take the gene therapy immediately, suggesting that such a sweeping change would not go over well so quickly.