Trans, Gay and Depressed

So the closest analog I think we have to sculk is slime mold. It spreads in a similar way, and there are a few species that glow under UV light.

I think their life cycle would function like this: - Sculk spores float through the caves, invisible to the human eye - If they find a suitable surface (porous, damp, dark), they'll start multiplying and eventually grow into a sculk vein (already an in-game item) - The vein continues spreading until it grows into a sculk colony (solid blocks of sculk) - After a colony reaches maturity, it forms a fruiting body known as a sculk catalyst - The sculk catalyst releases more spores, before blooming into either a sculk sensor or sculk shrieker (dependent on many environmental factors)

Sculk sensors detect movement via electrosensitive pores on the tips of their tendrils (similar to the methods that sharks and crocodilians use to sense prey). When they detect movement, they send an electrical signal through the mycelial network to nearby colonies. Sometimes, those signals reach a shrieker. Shriekers send out a pheromone gas (which hisses as it's released, hence the name "shrieker") to signal the sculk's defense mechanism, the warden.

The warden is a reptilian creature that survives off of sculk and occasional prey, such as bats (or players). It's able to subsist off of this lean diet because it spends most of its time brumating. (Brumation is like hibernation+ . Look it up, it's cool.) It has electrosensitive pores on its snout, sculk sensors on its head, a very powerful vomeronasal organ, and large eardrums. These give it an extremely adept sense of smell and very keen hearing. When it detects prey (or a threat), it uses its infrasonic vocalizations to incapacitate them.

Their mutualism is somewhat accidental. The sculk warning pheromone lets the warden know that prey is nearby, and in turn, the warden removes a potential threat to the sculk. The pheromone is meant to scare things away, but in the warden's case, it has had the opposite effect. But the sculk continues to thrive and the warden continues to eat, so I suppose nothing will change any time soon.