Campaign plot advice needed!

[Gilladian]

Given the geography, a river-spirit could make a lot of sense.

What did you have in mind for the Reflection Pool? If something there likes the occasional human (or demihuman) sacrifice, and could have extended its influence to the old battleground, that could add up to a pact with some dark overtones.

I had nothing in mind - it was just a toss-away spot that the PCs might investigate at some point and I'd probably come up with something on the spur of the moment.

But yeah, I was looking around and found a "Spirit of the Land" in the MMII. It's quite powerful, especially for an E6 campaign (tons of high level spellcasting ability), but definitely the sort of fey I was looking for. If it required a sacrifice every 5-10 years, that might explain why the King of Valencia was eager to convince it to move out here away from his kingdom! It may use the Reflection Pool as its "home" locale. And then when people come swimming, it occasionally "takes" one. Eventually the PCs are bound to go investigate, especially if someone of interest to them vanishes.

The Spirit will know that the 100 years is up, and has thus stopped doing what it doesn't really CARE about - guarding the Temple site from intruders, and also may no longer feel that ONLY taking sacrifices that "come to it" is required. Now it can pick and choose who it wants, where it wants, maybe. OR, it is ready to move on again, to another more isolated place, but it needs a guide to help it find said place. Or both. Maybe it takes the sacrifices to make itself strong enough to rip free of the land and move. I'll have to think about it.

Another possibility is the Verdant Prince from MM IV but it is outright evil, which may be too much for the region; an evil temple ruins AND a major evil fey?