You need an energy source other than the sun. The main alternative is reduced sulfur that can be oxidized for energy. Organisms that can do that chemistry are chemotrophs and so far all are bacteria. Either the bacteria themselves can form the plantlike base of the food chain or larger organisms with symbiotically associated chemotropic bacteria can be the base. Or both!
Snottites are the thick mucoid colony structures formed by cave dwelling chemolithotrophs which get energy from dissolved sulfur compounds in the water. From link
The snottites provide a food source for many fish and other insects
that live in the cave. One insect in particular that uses the
snottites as a food source is the midge that lives in the cave. The
midges lay their eggs on the snottites so that the larva can use the
bacteria as their main food source.
These worms in Colorado’s Sulphur Cave are believed to live on the
chemical energy in the sulfur in the cave, similar to deep-ocean tube
worms. On the left are streamers—colonies of microorganisms similar to
those in hot springs in Yellowstone National Park. PHOTOGRAPH BY
NORMAN R. THOMPSON
I am suspicious that these worms might actually just be grazing on bacteria. But maybe they do have chemotropic bacteria colonies inside them, like the tube worms.
Amphipods with chemoautotrophic exosymbionts.
I learned the word "exosymbiont"! These live in the Frasassi caves in Italy; interestingly the Wikipedia article on these caves does not mention what is practically exobiology; Google hits only scholarly articles. These amphipods are covered with filamentous sulfur metabolizing bacteria, which form their food source.
Niphargus ictus is the numerically dominant macroorganism in the
sulfide-rich Frasassi cave ecosystem and has been the sole amphipod
species reported to date from this location [14, 29, 30]. It thrives
in the sulfidic streams and pools found in various parts of the cave,
and a possible explanation for its tolerance to sulfide may lie in its
symbiosis with chemoautotrophic sulfur-oxidizing bacteria of the genus
Thiothrix . Such chemoautotrophic symbioses are common in marine
environments , but appear much rarer in freshwater where the N.
ictus symbiosis is the only example reported to date.
An interesting side note as regards the "aura". Hydrogen sulfide (H2S) is the reduced sulfur molecule which is oxidized for energy in these sulfur ecosystems. H2S is a toxic gas which smells horrible to us - like rotten eggs. The amphipods shown above are unusually resistant to H2S. I could imagine they might be attracted to it since that is what their exosymbionts and food live on. Maybe that is what the bacteria get out of the deal - in exchange for providing a food coat for the amphipod to graze, the amphipod can smell out H2S and move towards it so that its coat has food. Maybe your aura is H2S? Science is cooler than magic!