This is a rather short summary of events for a story challenge for those willing to try and take it up. At a latter date, I might release a rough script or summary of how I'd personally approach my own challenge, but any interested authors in question won't have to follow the script or can take or ignore any elements they choose if they want to.

The crossover challenge is, in the briefest of summaries, to take the Tartaros Arc of Fairy Tail and recreate it with the roles of the ten Tartaros demons being filled by the ten Espada Arrancars (such as Grimmjow killing the Magic Council instead of Jackal, Szayelaporro taking over for both Koyuka and Sayla by experimenting on Mira, torturing Erza and controlling Elfman, ect).

Espada ranking system would be the same (even if Baraggan is leader, he'd have to admit Starrk is stronger then him power-wise - or at least in terms of the pure quantity of power).

No constraints on one side needing to be the victors unless you want them - Arrancars might be the "antagonists" here, but it doesn't mean the writer has to make this a story where Fairy Tail wins. In fact, based on what I know of Bleach powers, I personally (and I do mean personally - as in personal opinion only) think that the Arrancars could probably one-shot the majority of Fairy Tail characters unless every single guild - including Dark Guilds and the Alvaraz Empire - worked together against them.

So either write a story where Fairy Tail has to unite with every other wizard to combat threat, or make it an outright death-fic with everyone on one side getting butchered - just so long as people stay true to what each character's capable of.

If you feel brave enough to try it, you can also try to add in more Bleach characters or the like, though for the sake of being concise I proposed the challenge with just a single one of the Bleach casts - the Arrancar characters - be used to start with. If there's any takers, let me know via reviews - or hell, even if anyone just thinks this idea has merit of some form, leave a comment.