Mercenaries is an action game released for Xbox 360 in April 2018. Recent coverage indicates the game has become integrated into Path of Exile's core content following an announcement about the new Curse of the Allflame league. The integration brings Mercenaries alongside other significant changes, including a fresh Ascendancy class and modifications to endgame progression and gem socket mechanics. Deep-sea exploration content also accompanies these updates, expanding the available activities for players.
via MMORPG.com
In this new league, there'll be some deep-sea exploration, the return of Mercenaries to the core--and a new Ascendancy with it--and endgame and gem socket changes.