Rarity and curses
Rarity runs Common, Uncommon, Rare and Very Rare, with separate Quest and Side Quest tiers for story items. Cursed items can't be taken off once equipped. The Black Candle lets you remove other cursed pieces but stays stuck itself, and a cat with the Blessing of Glorg disorder can unequip cursed gear freely.
Fragile and Brittle
Two keywords decide how armor dies. Fragile pieces break when the wearer is downed. Brittle ones have a 25% chance to break every time you take damage, which makes the Alloy set bonus (no more Brittle) a bigger deal than it looks.