Set in the future, players control members of the Tenno, a race of ancient warriors who have awoken from a century-long cryosleep as they return from a stellar system known as the Tau system after being driven back centuries ago in an ancient war. In the Solar system, they find themselves at war with the Grineer, a matriarchal race of militarized and deteriorated human clones built upon metal, blood, and war; the Corpus, a mega-corporation with advanced robotics and laser technology built upon profit; the Infested, disfigured victims of the Technocyte virus; and the Sentients, a race of self-replicating machines made by a long-dead transhuman race known as the Orokin. The Lotus guides the Tenno through difficult situations, as well as gives hints which help the player defeat enemies. To fight back, the Tenno use bio-mechanical suits, the eponymous Warframes, to channel their unique abilities.
All of the factions encountered in the game, including the Tenno, were created by or are splinter groups of the old Orokin Empire, which the Tenno learns was an ancient fallen civilization and former reigning power in the Solar system. Although most of them are long dead by the time of the Tenno’s awakening, their lingering presence can be still be felt throughout the Solar system. Before their fall, the Orokin had attempted to conquest the galaxy and sent out colony ships through the Void, a trans-dimensional space that enabled fast travel between stellar systems. None of these residental ships returned, and those they had loaded with Sentients returns with the Sentients now programmed to wipe out the Orokin, leading to the fall of the Empire.
In the game’s “The Second Dream” quest which was introduced in December 2015, the player discovers that the Lotus is a Sentient, rebelling against the others to protect the Tenno knowing of their importance. The Lotus’ father, Hunhow, sends a vengeful assassin called the Stalker to Lua (the remains of Earth’s moon), which the Lotus had hidden from normal space, to find its secret. The Lotus dispatches the Tenno there to stop the Stalker, arriving too late as the Stalker unveils the entity that the Lotus had protected: a human child known as the Operator, who is the real Tenno controlling the warframes through the course of the game. The Operator is one of several Orokin children that survived the passage of the Zariman Ten-Zero residential ship through the Void, the adults having all gone mad from its travel. When the ship returned to the Orokin Empire, the children had all been put to sleep for thousands of years, outlasting the fall of the Empire, to be found by the Lotus and becoming the Tenno (Tenno short for the “Ten-zero” of the ship’s name). The power of the Void gave these children the power of Transference to be able to control the Warframes from afar, making them the powerful weapons in battling the ongoing forces in the Solar system. From this point forward, the player can then engage in quests both as the Warframe and the Operator.