A way to get rid of the excess items is soon coming to the game.
The way it works is simple. You put an item that you picked up during your adventures in the dungeons into the Disassembler, and the Disassembler will provide you an ore of the same rarity as the item that you are disassembling. The ore amount depends on the tier.
An example, if you're disassembling a tier 3 rare longsword, then you will receive 3 rare ores.
Preview of the disassembler
I might add a way to "Mass Disassemble" items so that every item in your inventory with a specific rarity gets disassembled instantly, though I'm not sure if that's exactly a safe thing to implement so I'll be keeping an eye out for this.
Don't forget to Wishlist Nefarium to keep up to date with its development!