Talk:Excalibur/Umbra/@comment-178.87.153.218-20180705233144/@comment-31664784-20180706020110

From what I can tell, the Umbra design incorporates "Anti-Sentient" Technology. I think the lore implication goes something like this:

Prime Warframes are the original designs of Warframes, incorporating advanced Orokin technology and irreplacable components. The "default" Warframes are the approximated/worn down versions of these frames; having lost access to Orokin tech, the Tenno had to replace damaged parts with what could be scavenged or easily built.

Umbra Warframes are likely the "Next Gen" model intended for Warframes. After thoroughly analyzing combat data between Operators and Sentients, the Orokin started to produce Warframes that could better handle against Sentients. However, because the war ended (or perhaps because of the Tenno uprising) soon after their production began, the models where never properly introduced and were left to fend for themselves.