In the Metamorph league, you'll meet a new NPC, Tane Octavius, a master alchemist who studied in Oriath. Exiled to Wraeclast for killing his teacher, Tane searches for what makes the "self", by using his learned alchemical knowledge to assemble monster essences. He hopes to find a cure, or perhaps just the source, for what he calls "the intrinsic darkness" that led to his unforgivable violence.
In each area you play in the Metamorph League, Tane will collect samples from selected monsters you have killed. Summon Tane to combine your choice of samples to create a formidable Metamorphic foe to defeat. Each sample contributes abilities to this boss, who wildly morphs from form to form during the encounter. With careful selection of samples, you control which abilities the boss has and what rewards it yields.
Metamorph encounters can also drop Catalysts, a new type of currency item that adds quality to jewellery. There are many types of jewellery quality, each related to a set of mods. The quality value on a piece of jewellery scales up the magnitude of related mods on the item and can be consumed through crafting to increase the chances of rolling related mods.
In the endgame of the Metamorph league, you can collect samples from Maps Bosses to create deadly Metamorphs that combine the powers, challenge and rewards of multiple bosses into very dangerous encounters.
The Metamorph league is part of the larger Conquerors of the Atlas expansion, coming out on December 13 (PST) on PC, and the following week on Xbox One and PlayStation 4. For more information about Conquerors of the Atlas and its new systems, click here.