The Warriors (戦士 Senshi?) are an organization of humans from beyond the Walls who can transform into Titans. They want to take the "Coordinate," which is currently inside Eren Jaeger, and bring it to their hometown.
For reasons unknown, the Warriors act with the intent of destroying humanity within the Walls. This mission began in the year 845 during the fall of Wall Maria and has been ongoing for the past five years. However, Warrior Reiner Braun has claimed that after the discovery of Eren Jaeger's Titan power, this aspect of their mission is no longer necessary as long as Eren agrees to return with the Warriors to their "hometown."
The Warriors have been extremely secretive due to the nature of their mission. For five years, the identities of the Warriors who began the attack on humanity remained unknown until Annie Leonhart was the first to be caught. The remaining two Warriors, Reiner Braun and Bertholdt Hoover, were only discovered to be enemies of humanity after a link was discovered between them and Annie. Despite apparent friendships formed with their comrades, the Warriors nonetheless follow their true duty without question.