Threads drop for ten mechanics (Abyss, Blight, Legion, Breach, Incursion, Betrayal, Bestiary, Expedition, Ultimatum and Ritual), and up to eight can be spent on one mechanic at the map device; finishing the Atlas quest line opens three thread slots, so up to three mechanics can be guaranteed per map. Scarab effects move into a rebuilt Atlas passive tree, Mirage becomes a core mechanic, and mechanics now interact.
Loot changes too: magic and rare drops roll tiers, monster rarity rather than item quantity drives rewards, and the hardest rare and unique monsters become the main source of Divine Orbs. Sources: OutputLag (6 November) and PCGamesN (7 November) on the keynote.