Errtu's Revenge; Drow/Fey'ri alliance?

[j_spencer93]

I am working on a campaign for very small group (hoping to pull more in) and know that most of the players are a fan of elves. So naturally i wanted to make Drow their foe, however, having read R.A.Salvatore's books I think that is done to death (atleast for me). Instead I wanted to pull the Daemonfey into it and noticed the wiki mentioned they are not opposed to allying with the Drow if needed. So;

What sort of situation or goal would cause these two to ally? And what could their endgame possibly be?

I thought of having a Le'Shay appear and offer to restore their races to power if they followed him into a new Crown War but thought maybe that was to bland, so fishing for ideas.
Even thought of maybe an elven/dragon rider thing but it didnt really pan out realistically. The story felt forced.

[gfishfunk]

Invent a magic item of legendary quality that does the adventurers no good but is incredibly powerful for a people group.

The elves have a magic item - The Horn of Spring (or somesuch) that protects their harvests from rot. The Daemonfey want the Horn, either to increase the presence of rot for nefarious fey purposes (maybe they can harness the power of rot) or to protect their own crops.

[j_spencer93]

Actually not a bad idea. Not sure why I didn't think of something similar. Although i am not sure if thats really a reason the Drow and Fey'ri would make an alliance....was thinking of something involving High Magic (i know, its not in 5th edition).
Like what if their was a way discovered for them to use it but it was guarded by Evermeet or something....something neither race could take on themselves.
OR
What if Errtu was summoned to mate with some high ranking Deamonfey, and got the idea to conquer the material realm at the behest of the BBEG (le'shay), and thus drew upon his knowledge of Drow and recruited any he could find into Hell's gate to create Draegoloth's. That would fit thematically and would tie it into a story two of my player's really like. Also would tie it into an older campaign i ran where Errtu absorbed a good portion of Eltab's power.