Who is the Stalker in Warframe?

destructoid.com:

Everyone’s favourite grumpy assassin is back in the Jade Shadows story update for Warframe, and he’s more tragic than ever. But who is this enigmatic figure, and why is he at the centre of the latest mystery in Warframe’s epic narrative?

Take care Tenno! This article contains spoilers for Warframe’s story, including Jade Shadows.

The player character first encounters the Stalker when he sends an ominous message after they have killed a high-profile assassination target. You are marked for death, and with a dramatic entrance of red flickering lights and coiling black smoke, the eerie figure of the Stalker emerges into the middle of a mission, ready to carry out his assassination. Early on, he is a daunting challenge, with unearthly speed and a range of cruel weapons named very normal things like Despair, Dread and Hate.

The Stalker wears Tenno armor but the true nature of his connection to the Tenno is still occluded. At first, the Stalker seems to be a lone assassin seeking revenge on the Tenno for their destruction of the Orokin Empire, but over time it becomes clear that he has made a powerful alliance.

When Tyl Regor seeks to excavate the Sentient Tombs on Uranus, he accidentally releases a powerful Sentient called Hunhow, who offers an alliance to the Stalker in a plan to destroy the Tenno. He bestows the greatsword War upon the Stalker and dispatches him as his agent, newly transformed through Sentient technology into the Shadow Stalker. The Stalker learns that the source of the Tenno’s power is the Reservoir on Lua, hidden away in the Void by the Lotus, and plans to collapse the Void around Lua to destroy it. With the help of the manipulative Corpus Alad V, the player character drags Lua out of the Void into material space to frustrate the Stalker’s efforts. The Stalker learns of the true nature of Tenno, controlled by an Operator, and questions the nature of his own existence.

The Stalker sends out his Acolytes, Angst, Malice, Mania, Misery, Torment, and