The Forgotten Sanctum, the third and final paid expansion for Pillars of Eternity 2: Deadfire, will be released 13th December.
Forgotten Sanctum will send players on a new adventure at the behest of some Archmages, one of which has gone sour and caused a load of problems. Within this wrapper you'll do what sound like some fun things: explore a dungeon built into the flesh of a sleeping god (doesn't say who), eww yuck, and overcome the highest-level challenges yet added to the game.
The Forgotten Sanctum costs $10/ 7.50 alone, or is included in the season pass with the other expansions Beast of Winter, and Seeker, Slayer, Survivor.