Excalibur/Umbra

Excalibur Umbra is the Umbra variant of Excalibur, first released in the Chinese build of WARFRAME. It was released in the Global build in, and can be acquired through The Sacrifice quest.

Acquisition
The blueprint for Excalibur Umbra is given to players upon completing the first mission of The Sacrifice quest, and the ability to build the Warframe is granted on completing the second mission. Unlike other Warframes, Umbra requires no further components and is constructed entirely from the single blueprint. However, even after being crafted, Umbra cannot be used until the penultimate mission.

When completed, Excalibur Umbra will already be maxed out at level 30, pre-installed with a free Orokin Reactor and Warframe slot.

The Sacrifice
Excalibur Umbra was originally a human, an Orokin Dax soldier who was punished by Ballas for attempting to interfere with his betrayal. The soldier was deliberately exposed to the Infestation to become an anti-Sentient weapon, then psychologically tortured into rote obedience by forcing him to kill his son, Isaah.

As a result of Umbra's torment, he retains most of his sentience and is capable of acting on his own without the Tenno's control, even initially rejecting the Operator's Transference and going rogue. Umbra also carries the memories of his final moments before transforming into a Warframe, which the Operator discovers to contain codes that unlock Ballas's Vitruvian recordings of the Sentient's betrayal, the creation of Warframes, and the Tenno.

After seeing all of Umbra's memories, the Operator reassures Umbra that they will fight Ballas together. Upon seeing this act of compassion, Umbra calms down and finally accepts the Operator's Transference.

Trivia

 * Umbra is the Latin word for "shadow".
 * Excalibur Umbra is the first Umbra variant of a Warframe to be released in WARFRAME.
 * Excalibur Umbra is the only quest Warframe that cannot be purchased from the Market, nor can he be sold.
 * In the Chinese Build, Excalibur Umbra originated as part of their Founder's pack exclusive, named as Excalibur Umbra Prime. The pack also included the Nikana Prime and the Spira Prime (both of which were introduced in the Global Build with Saryn Prime instead), as well as the Gauvan Prime Sekhara, a shoulder accessory obtainable only through that Founder pack.
 * Umbra uses a different sword design for his Exalted Blade, which is named Exalted Umbra Blade. The stats for both weapons are identical however.
 * Upon completion of The Sacrifice quest, players will receive an Excalibur Umbra exclusive Excalibur Umbra Sunder helmet, which is a battle damaged version of the regular Umbra helmet.
 * When interacting with Baro Ki'Teer, Baro will treat Umbra condescendingly, as he would any other non-Prime frame.
 * Exalibur Umbra is the first Warframe confirmed to originally be a human. It is also the first frame to have had its face exposed due to damage to its helmet.

Bugs

 * After Excalibur Umbra is equipped for the The Sacrifice, one may still use him prematurely by not equipping another Warframe.