The "blood" of many of the cryx creations appears to be a phosphorescent green liquid that has both alchemical and necrotic (negative energy) properties.  The liquid seems to be able to power the cryx creations, though it dissipates over time and they must be re-energized with the liquid.  As the liquid degrades it seems to turn into a gaseous state and this may explain the strange green mist that surrounds many of cryx in their lairs.  The liquid and mist have a strong acrid and metallic smell to them.  The liquid burns extremely cold when it touches flesh and these acidic and cold properties maybe why cryx have an immunity to acid and fire. The mist also seems to lower the ambient temperature around it explaining why Cryx lairs are often bone chillingly cold. The exact method the Cephelix use to create this liquid is unknown.  The liquid does radiate a powerful necromantic magical aura.