I like the idea of the required weapon similar in style to say, the spook smasher. Perhaps it could be a set of items such as [cursed muramasa] (weapon), [Wicker of inight] (helm), [Ronins Garb] (armor), but rather then be purchased, you'd have to get the recipes from the brothers and hunt some [cursed scouts] or the like to get a few bits and bobs to make the gear since they would be crystaline themselves (albiet undreakdownable).
It would draw out the event a bit and add a bit of an anoying step sure, but i think it would liven things up as well rather then be a "go kill tons of stuff" or "here, buy this and go kill tons of stuff" lol. not that im saying the current globals are bad, just saying that a slightly newer goal would be cool to see
edit: also, he bits and bobs should be bound o3o everyone should earn their reward lol