80 uniques: one of a kind, and they know it

How the 80 unique items in The Ember Depths work: class weapons, archetype armour and jewelry, powers that change how you play, attunement and where they drop.

Uniques are named, one-of-a-kind items with fixed stats and one or two powers that change how you play: echoes, summons, chains, curses and worse.

Class weapons for every class, armour and off-hands for each archetype (Vanguard, Devout, Skirmisher, Arcanist), and jewelry anyone can wear.
Attunement: stats always apply, but only so many powers are active at once: 1 from level 5, 2 from level 10, 3 from level 20.
Where they drop: Your first boss kill at level 5+ (a weapon for your class) · any foe from level 10 (bosses and elites far more often) · first kills of the Act III–V finales · rarely a Mystery Cache · Tavern Unique Contracts.
Your first unique is guaranteed: a weapon for your class from your first boss kill at level 5 or higher.
Uniques get their own beam on the floor, are always picked up, and (since 0.4.2) come home through Lost & Found if you leave one behind.