Kairn

 The Kairn are a silicone based species (silicate) that achieved high technology around the same time as the Queldari.  They appear as ten foot tall crab like beings with a crystal like exoskeleton varying in color depending on the types of minerals the Kairn has been consuming.  The Kairn originate from an entire ecosystem of silicate beings, of which they are the most successful and intelligent.  

Silicone based life is rarer than organic life, but still fairly common, there are a large number of intelligent silicate species on a vast number of worlds.  Silicates in general are fairly similar to organic species, however they vary in a few key ways.  One is the types of minerals required for silicone based life are far more common on most rocky planets, and therefor means the silicates inherently have access to a huge amount of material resources.  They basically eat processed rock.

Silicates use hydrofluoric acid chemically in the same way we use water, effectively meaning their blood is an incredibly powerful acid, many silicates also spit acid.  The exoskeleton of a Kairn is made of fused rocky mineral plates, making it super hard and pierce resistant, the exoskeleton can however be shattered by concussive force.  Their rocky shell and silicone chemistry makes them especially fire resistant. 

In the times when the Nergal swarmed through the universe unchallenged, the Queldari and Kairn worked feverishly in secret to prepare for a day when they might challenge the supremacy of the monstrous Nergal.  The Queldari ultimately struck first and began their crusade