The twilight euryptile has changed little from its ancestor. It still maintains the same body shape. However, unlike their ancestor, the twilight euryptile is grey in coloration, allowing it to blend in with the grey sand in the twilight zone. However, this coloration is only useful when hunting down prey that uses bioluminescence, as the dark waters make it hard for sight to function. Because of these darker waters, the twilight euryptile has developed chemoreceptors that allow it to detect traces of waste, blood, or any sort of substance prone to dispersing into the water. These chemoreceptors are situated on the inner edge of the claws. The final pair of legs on the twilight euryptile have become broad and flattened, increasing the combined surface area of the leg and fin. However, this makes the final pair of legs harder to walk on.
The twilight euryptile's behavior has also changed little from its ancestor. It still lies in wait for prey to come too close. However, the twilight euryptile spends more time swimming than its ancestor, allowing it to access prey in the water column. They typically pursue twilight gills, which are large and undefended. This makes them easy prey. Large kills like the twilight gill are dropped down to the sea floor, where the twilight euryptile will gradually eat away at the corpse until nothing is left. The twilight euryptile will opportunistically feed on any scavenger that attempts to steal its kill. This primarily manifests in it attacking intruding segmolixos and shoals of greenscale cish. Twilight euryptiles most commonly feed on soft-bodied organisms, as their jaws have trouble crushing the exoskeletons of organisms such as the clawface siluro.
When two twilight euryptiles of the opposite sex meet each other, they will almost always attempt to mate. This is because the twilight euryptile population is sparse, and mates are hard to find. The male will first court the female by presenting her with a large carcass that she can lay her eggs in. The male will then fertilize the eggs. After the encounter, the male will guard the carcass while feeding on any scavenger that comes too close. Once the eggs hatch, the male will abandon the carcass. The young will then consume the carcass and begin hunting for small prey, such as lagnodactyls and more primitive asterzoans. As they grow larger, they will then feed on small gelataventrians, before finally feeding on larger gelataventrians and asterzoans.