Drider

 While they bring a lot to the fray with their stat block (some decent spells, venom, thrown webs), the true terror of a drider comes from their disgusting origin. But fleshwarping is mostly tied to the drow... and what if your world doesn't feature drow, or features them in a positive role? These following encounters will try to explore driders as true abominations, while giving you multiple ways to play that sense of degeneracy.

Pyottar Pakhar was a mad elven scientist and alchemist, whose goal was to hybridize humanoids and animals. Running out of both willing and unwilling subjects, he conducted his final experiment on himself. He exposed a spider to the wild magics of the Magicka Wastes, and then had that spider bite him. While the experiment was a partial success, giving him a spider's legs, as well as the ability to scale walls and produce webs, it also backfired. The former genius is now reduced to an almost bestial level of intelligence, instinctively guarding his old lab. The fact that the lab contains a potion rumored to stop aging has given him ample opportunity to feed.

In the netherspace, driders aren't created - they are instead a parasitic species. The vile spider-beings' larvae travel between planets on asteroids, embedding themselves in soil, and finally reaching their humanoid hosts through nutrition. Once ingested, the larvae wake up from dormancy, and quickly produce spider-like growths on the infected's bodies. The nervous system is the last to be attacked. The growths can somewhat safely be removed before the host kills for the first time - but a taste of fresh blood awakens a deep frenzy in the beings, sealing their hosts fate.
While individually dangerous, the spiderlike parasites have been treated as a pest for years - owing to the fact that they appear to posses no true nervous system, and no real agenda. That belief is put to a test when a group of smuggler accidentally discovers a planet absolutely overrun with driders, who seem to be gathered around massive, organic, pyramid-like structures.

The mysterious driders have been engaged in a war with elves for eons. When a renegade squad of them comes to an elven redeemer, asking for a chance at breaking the "cycle of curses", the elf is slow to trust them, but willing to hear the story. The driders reluctantly agree to show the redeemer the "sacred sacrificial altar", where supposedly everything will be clear.
Unfortunately, that same night, their camp is attacked - by beings similar to the driders, but with the lower bodies of massive scorpions instead. Only the elf and his squire make it out with their lives. They are now faced with the question of a lifetime. Is the secret that could end the cycle of violence worth risking their lives?