I’ve become interested lately in designing creatures that require feeding on mental/psionic energy rather than material matter to live.
Elgazers are a small species of psionic predator. The “eye” is actually a complex feeding organ. It emits a beam of psionic energy at the target that acts on the mind like digestive juices, unraveling the target’s cognition. The elgazer follows the prey until it is incapacitated and then draws in the partially digested psionic material through the feeding organ. They may attack fully sapient beings in self defense, causing lapses in cognition which can lead to permanent damage of the psyche if left untreated.