Warframe Lore - During the Old War

The Old War is a battle sided in the Sentients favour. This is because of the Sentients ability to assimilate and adapt to the Orokin's Weaponry. Furthermore, the Sentients can withstand death itself due to them somehow acquiring Oro. An early attack on an asteroid mining facility on the outer terminus leads to the discovery of the Sentients inability to assimilate to archaic weaponry. The Grineer Slave who incidentally discovered this is used for future cloning batches of the Grineer.
 * 1) It is speculated that the Sentients gained Oro from their unprotected journey through the Void, much like the Tenno did.

Due to the Sentients ability to resist and assimilate highly technological weaponry, other avenues of combat are explored. One of which being known as the 'Technocyte super soldier' experimentation. It is speculated that the Warframe Nidus was one of the golems created in this experiment. The Technocyte project fails due to the golems being uncontrollable, but it is later discovered that the children of the Zariman Ten Zero can interface with the golems through a process named 'Transference'

The Archimedean Sylvanus, tasked by the Orokin to recover Earth from the Technocyte infestation, was recruited by Margulis to assist with the children of the Zariman Ten Zero and help with the Transference therapy. Sylvanus and Margulis are assigned to the 'Warframe development project' and are tasked with creating new forms of destruction for the children to wield. This task causes Sylvanus immense grief and causes her to plot against the Orokin. The Orokin continue to pressure Margulis to abandon the children and turn them into weapons of war. in her rage, she denounces the Orokin and thus for her crime of apostasy, is sentences to death by the Executors, one of which is her lover, Ballas.

The Transference project leads to a turn in the war time efforts and the Sentient forces are driven back. The Zariman children, now called Tenno, are hailed as saviours. These Tenno founded the great schools of Naramon, Zenuric, Unairu, Vazarin and Madurai

In attempt to profit from the salvage of war, scattered mercantile guilds and scavengers joined together in a cult-like religion that worshiped profit. This faction was called the Corpus. This cult is denounced by the Executors and deemed an enemy of the Empire.

Sylvanus, experimenting with artificial transference, abandons the Orokin and flees to Earth. Using her apothics and custom somatics she attempts to link with a terraforming forest and bring it under her control. This process rends her mind from her body and leaves her stranded within the forest itself.

Meanwhile, Rell, having survived his experience on the Zariman Ten Zero, plots in secret to combat an entity in the Void who he refers to as the Man in the Wall. Rell believes this entity is an embodiment of the Void its self - a timeless, uncaring, all-seeing consciousness  that watches our dimension from beyond

A mercenary soldier by the name of 'Ordan Karris' was hailed by the Orokin for the genocides he has committed in their name. They award him the honour of an absolution ceremony. Ordan, wrought with the horrors he has committed, plots a suicide attack to kill them with concealed bone plugs in his neck and atone for his sins. However the Orokin Elite were anticipating this and laugh at his attempts to destroy the immortal. As punishment for his transgressions, his mind is converted into a digital being known as a Cephalon and is placed in an Orbiter compartment as an aid for the Tenno Operator. The memories of his past have been wiped clean by the Orokin and Ballas and he becomes Cephalon Ordis.

In an attempt to regain the upper hand in the war the Sentients devised a plan to have Natah, daughter of Hunhow, infiltrate the Empires hierarchy and destroy the Orokin and the Tenno from within. Though she succeeds in infiltrating the hierarchy, as she learns of Margulis and her actions, her own sorrow at becoming barren from crossing the gap between Tau and the Origin System drives Natah to become the Lotus. Taking on Margulis' appearance and mannerisms.

As the war progressed, Ordis begins to see fragments of his old self resurface in his mind but stifles them to protect the Operator. At around the same time a Sentient attack on the last Orokin tower on Earth is repelled by Gara. The remains of the defeated Sentient are kept dormant by an Orokin technology that cages the remains within. This land later becomes known as the Plains of Eidolon.

At some point around this time. The twin queens are born to an elder Orokin. They are initially sentenced to death for their twin-ship. But are spared by their father

The Sentients devise a plan to initiate a false retreat and Hunhow allows himself to be destroyed above the seas of Uranus. His plan being to have his daugher, Natah, revive him and mount a surprise attack. With the death of the Sentients leader, Hunhow, the Orokin believe the war to be over.