Long term project. Not sure if it's been breached.
A lot of other games have 'set' items.
Why not incorporate a version of it in this game?
It wouldn't be all midnight dragon eq or anything like that...but things you want to figure out.
IE Sword of Darkness + Shield of Darkness gives you X.
Something not too strong (maybe a reduced frenzy or a reduced protection versus light or something).
Or like 5 items of different combination gives you perma pass door.
Or maybe even a set item gives you the option to say a word that you can do occasionally (like the orbs in the elemental temple) that gives you an affect.