“You're not supposed to be in here! You're going to ruin the surprise!”The following section contains spoilers.
Teshin is the Conclave Master, who resides within the Conclave Hall of the Relays. He is responsible for the management of the Conclave PvP System, providing incentives through various rewards that can be earned through Conclave battles.
Teshin is an individual from the Orokin era, who was one of the few who did not enter cryosleep. How he has remained alive for this long however, is unknown. He blames the fall of the Orokin on the Lotus, who led the Tenno to become complacent like oxen.
Teshin references the imminent arrival of the Sentients by insisting the Tenno use the Conclave to fight their greatest enemy, themselves, in order to grow stronger and to prepare themselves for 'horrors' beyond the Outer Terminus.
During the Natah quest, after the Lotus breaks off communication with the Tenno, Teshin makes contact, offering to guide the player and help them figure out why. By the time the Lotus resurfaces, the Tenno and Teshin are already hot on the trail of Tyl Regor and his excavation team.
Notably, Tyl Regor calls Teshin a "pseudo-Tenno," and implies at least some familiarity between the two.
During this quest, it is revealed that Teshin is a Dax soldier, bearing the epithet "Teshin Dax", one of the mighty warrior caste created by the Orokin and used as their personal guardians. Unfortunately for him, the Elder of the Grineer Queens possesses a Kuva Scepter, marking her as a member of the Orokin Elite. As result of his Dax heritage, Teshin is mentally incapable of refusing her orders, though his loathing for the Twins is made quite clear.
In the quest, Teshin suggests that Margulis did a disservice to Tenno by concealing and erasing their past. Partly to rectify this and partly to save the player's life, Teshin guides the player's Operator (via astral projection, it is assumed) through a mountain temple on Earth, to an Orokin Yuvan Theater previously used for countless Orokin Continuity rituals. Thanks to Teshin's guidance the player's Operator regains full use of their powers, and transfers into the Kuva Fortress using their Warframe. In the ensuing battle the Queens' Guardians and Teshin are defeated, and the Elder Queen loses possession of her Scepter, freeing Teshin from her thrall.
- His voice actor is Sean Phillips. 
- His helmet makes him look similar to a Kappa, a Japanese mythological water imp with a plate full of water on the top of its head.
- The style itself is also reminiscent of a kasa, a traditional Japanese hat commonly worn by monks and warriors.
- Teshin is the second syndicate leader to have multiple intro voice lines, with the first being Cephalon Suda.
- He wields a Nikana and a Nikana shōtō, both having Gemini Nikana Sheaths. He is also able to call his blades to his hands in the event he is dis-armed as indicated in the War Within quest.
- Teshin is likely derived from Deshin Shekpa, the 5th head of the Kagyu school of Tibetan Buddhism.