As a twist on "Evil Druids", here is a circle of druids I have developed for
Urbis:
"The Circle of the Crumbling Tower
The druidic faith as a whole is under retreat. The rulers and merchants of the city-states do their best to divide the receding wilderness among themselves, and any druids who dare to stand in their way are killed as often as not. As a result, most druids feel nothing but hatred for the rich and powerful of modern urban society.
Still, there is something that druids have that is of interest to many of these same rich people: The ability to cast the reincarnate spell. While magic that is capable of bringing back the dead is fairly easily available to anyone who can afford it, these spells are incapable of bringing someone back who died of old age. While the reincarnate spell has to abide by this limit as well, it is capable of reincarnating anyone else into the body of a young adult. Thus it is possible to prolong one's life span almost indefinietly with repeated application of this spell. The fact that one is usually reincarnated as a member of a different species is a small price to pay for those who are desperate to stave off old age.
Unfortunately for such would-be immortals, druids regard such use of this spell as a perversion of nature, and they cannot simply be bribed into casting it, unlike many clerics. It doesn't help that many of the people who ask them for help are the same people who despoil nature as a part of their normal businesses. And most people would rather die than give in to threats that would make them help the enemies of their faith.
But in 1387 NA, a young druid named Garin had an idea. Instead of allowing themselves to be bribed for this spell, he argued, the druids should demand favors for this service. After all, many of these who approached them were some of the most influential people of the region, and their power could easily be used to further the druids' agenda. And if they didn't keep their word, they wouldn't be able to get reincarnated in the future!
Many druids considered his ideas to be blasphemous, but others saw their merit. And so, the Circle of the Crumbling Tower was founded. Its approximately 20 druidic members meet periodically near the Fields of Harrow, but are often abroad to check their city-based "charges" - the merchants, nobles, and other rich and influential people who sold out their freedom in exchange for a stab at immortality. None of the druids really trust these people, but the hold over their lives is powerful - it has become standard practice that anyone who betrays the circle is not only killed, but his body is hidden and his finances ruined so that he is certain to stay dead.
The people who have sold out to the druids are in a precarious situation. They need to remain in the favor of the druids, and that usually means sabotaging the orderly functioning of a city-state in some way - destroying crops, changing building plans to reduce the efficiency of nexus towers, sending bandits to waylay trains, and many other dirty deeds. But often this not only costs them a lot in money and resources, but even hinders their own business efforts. Most druidic handlers are willing to cancel an operation if the risks of discovery seem too great, and they usually will listen to the advice of their charges (after all, they know little of the working of a city), but anyone who constantly makes excuses for not doing anything to further the druidic cause will earn their displeasure. As a result, most charges come up with ideas on their own, and are desperate to please their handlers with reports of progress.
Sometimes, several charges conspire to keep their common druidic handlers ignorant, but these conspiracies are often betrayed from within, as one of their members blows the whistle on them to curry favor with the druids. Thus, most dependants of the circle are extremely paranoid about whom they trust. Those who have already been reincarnated face an additional problem: They have to explain their now different appearance somehow. Most invest in illusion or polymorph magic, and mostly retire from public view so that their true form doesn't become public knowledge. There are now several merchant houses which are now lead by someone reincarnated into the body of a young orc or kobold!
The circle has now about a hundred charges, and new ones are being recruited on a regular basis. The aged Garin, who still leads the circle, worries about the risk of discovery, but for now remains committed to the current path."
So maybe your elf decides that he needs to destroy human, city-building civilization. But he knows that elves alone are not strong enough for the task - and most of his fellow elves wouldn't even want to try that.
Instead, he seeks out aging but rich and influental humans, and offers them the following deal: Work for me, and I offer to
reincarnate you as long as I live (which can be a long time with an elf). All they have to do is figure out new ways of harming or even destroying human cities...
And there are always some who are desperate to take up that bargain.
