The Skeeves are a bunch of klartesh-smoking, nubile, attractive, totally sexless and seriously dangerous elf-like things that hang out in ancient wood groves and dungeon rooms-of-a-certain-size. As the party approaches, a smell of sex and resinous smoke is detected, but a male elf will smell the smells a long ways off if the party doesn't approach directly. A sentient creature with keen hearing can make out sighing, moaning, giggling, and slurping.
In the meantime, party members who did save have the odious task of dispelling the charm effect, by whatever means necessary. The most efficacious way is high wind, rain, flooding, or ice since these will undo the conditions that make the things so attractive (warm, smoky, cuddly, fleshy). In truth, the Skeeves are an elf-like race that preys upon the desires of adventurers and other sordid types. Bags of Doritos litter their lairs.
The Jeeves are a race of clockwork/steam/electric/organic/demonic/necormantic butlers. They secretly hate their masters, but will obey dutifully and to the letter of requests, especially if it will put masters in harm's way or transfer ownership/servitude of the Jeeve in question to a more powerful master. The never tire, never sleep, and need no food or water. The speed and cleverness of the Jeeve will depend upon their components: i.e. clockwork Jeeves are somewhat slow, uncreative, and wimpy. Organic and demonic Jeeves will be quite clever, malicious, and innocent looking but their beating hearts and sadistic eyes may give their intentions away. A Jeeve will follow any request it is given as long as the request will not effectively cause its own death, and it will obey gleefully if it will cause the death of its current master, and doubly so if the request is from the master in question.
Sometimes whole dungeons can be over-run with a nicely harmonic ecosystem of Jeeves serving Skeeves and their victims, and when equilibrium is threatened the homeostasis breaks and bonuses can be had to the Skeeves charm-effect saving throws and Jeeves will peel off to serve adventurers and redirect them to more imminently dangerous zones.