I feel like the unimplemented First Fractal would be a good fit. One of LC's main attacks is to summon clones of himself- exactly what the First Fractal does!
In fact, since we only have one other weapon Expert drop, from Skeletron (the other boss you fight in front of the Dungeon), I feel it'd be an even better fit!
If FF got buffed and added in, it'd be a great melee weapon for the pillars thanks to how it works. And well, it's better than nothing!
Alternatively: An accessory which turns your Mana pool into a shield of sorts. Depending on how much mana you have, when you're hit, part of the damage is taken from your Mana instead of Life. This would give Melee and Ranged a use for mana, and also give a larger survivability buff to Mage and Summoner, the two classes that need it most.