Sets give bonuses when you equip at least 2 parts of the same set and it's often better than wearing a full set. Examples include Tal'Rasha armor+amu+belt, Angelic amu+ring(s) or Death gloves+belt. Elite class-only sets like Griswold will give you yellow aura when you equip all the parts. You can buy extra sockets on product page, note that set items can't be upgraded.
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