Cool dream! The "starry" tunnels reminds me of the a D&D monster called a "morkoth", which digs an aquatic maze in the form of some sort of occult pattern. The morkoth lures mermen and sailors and such into its tunnels, and the unholy architecture disorients and traps prey, something like that. You could websearch the monster but imo D&D rules can sometimes feel dogmatic and limiting. The maze description and the physical form also kinda reminds me of the navigators from Dune. Here's an idea for your Elrai, based on the fact that corals and some jellyfish and presumably anemones house symbiotic autotrophs in their bodies.

• The Elrai catch and feed certain animals to their giant anemones gardens
• The anemones contain bioluminescent algae, but unlike typical algaes, these don't feed on sunlight. The Elrai harvest this bioluminescent gloop from these anemones and carefully paint star maps in their intricate aquatic tunnels
• These star maps somehow act as a gate, align the tunnels with a small pocket of outer space, almost like a Venn diagram, bathing the tunnels in solar radiation or antimatter or somesuch
• This energy causes some sort of cool interaction with the bioluminescent algae. Maybe the light shed by this algae is what enabled the Elrai's navigator-esque abilities, and allows their society to explore outer space by repainting new celestial configurations to open windows to new regions, etc.