They live for around 60 years.
Nymphs emerge from a primordial ooze as slimy, featureless humanoids with rudimentary sensory organs and a mouth, developing traits selectively as they consume prey. Their culture is largely tribalistic and utilitarian, with a reverence for hunting and a general rule of ‘might makes right’. Weakness is culled and discarded.
Each nymph has an innate desire to become an ultimate dominant being, whether through assimilation, fleshcrafting, or other means. Nymphs see other species in terms of food - some is better consumed, other is best left on the shelf for later. The suffering of other races is largely inconsequential. Nymphs don’t see themselves as evil because they don’t see other races as whole individuals, just collections of traits. The whole is not greater than the sum of its parts.
Nymphs remain as ‘solitary predators' even inside greater communities, preferring either self-reliance or tightly-knit groups of other nymphs. Nymphs avoid absorbing too many traits of a single species, seeing it as willingly taking on their flaws as well or risking becoming too much like their prey. Some nymphs develop tendencies to usurp the lives of their prey, essentially becoming them, taking over their jobs, families, and positions in the community, becoming like sleeper mimics.