Too Long; Didn't Read
Kuva Liches are part of a system meant to emulate Middle-Earth: Shadow of Mordor’s Nemesis system but with a Warframe twist. They are guaranteed to drop a beefed-up version of classic Grineer weapons or a brand-new one. Each weapon is distinct from their non-Kuva counterparts by having some nice glowy bits and by having superior stats and characteristics. They also come with a 20% chance to drop an Ephemra related to the element of the Warframe that killed them.