Did you consider the Spell Strategist set at all? It's got a dark purple visual effect that seems kind of on-theme for what you're aiming for, and the set bonus is fairly strong as well. Probably a better choice than War Maiden, since WM only boosts Magic Damage (as in, capital M capital D) so things like your Twilight and your Light/Heavy Attacks won't get boosted at all; whereas Spell Strat gives a generic Spell Damage boost that affects everything (but only against a single target at a time). Can't say for certain that SS is better than WM for your build, but I suspect so.
Looks cool either way, though! Always nice to see people breaking away from the absolute meta and making their own flavors!