The secret organization opposing Lara Croft in Rise of the Tomb Raider is Trinity.
Trinity is a powerful ancient order seeking the Divine Source, the artifact at the center of the game’s conflict. Lara pursues the same object because she believes it can prove the existence of a lost civilization and help explain her father’s research. This places her expedition directly against Trinity’s military resources and archaeological ambitions.
The organization is led in the game by Konstantin, who acts under the direction of the mysterious Prophet’s enemies. Trinity combines religious ideology, intelligence operations, and armed force, making it more organized than the scattered threats Lara faced on Yamatai in Tomb Raider (2013).
Players sometimes confuse Trinity with the Solarii. The Solarii are the violent island society encountered in Tomb Raider (2013), led by Mathias. Trinity is a separate organization introduced as a major threat in Rise of the Tomb Raider and expanded further in Shadow of the Tomb Raider.