Why it matters: Ghost of Tsushima developer Sucker Punch Productions revealed on Monday that it is working on a cooperative online multiplayer mode for the newly minted action-adventure game that'll ship as a free update by year's end.

Ghost of Tsushima: Legends is described as an entirely new experience. Whereas the base game features an open world with a focus on exploring the environment's natural beauty, Legends is said to be more haunting and fantastical and will concentrate on action and cooperative combat.

It won't follow protagonist Jin or characters from the single-player journey but rather, four other heroes - the Hunter, Samurai, Ronin or Assassin - that "have been built up as legends in stories told by the people of Tsushima."

Gamers will play in groups of two or four. With two players, you can expect a series of co-op story missions that grow in difficulty and require careful synchronization with your teammate. As part of a four-player squad, you'll tackle wave-based survival missions in a fight against the toughest enemies the game has to offer.

Sucker Punch also teased a four-player Raid mode that'll land sometime after Legends launches.

Ghost of Tsushima launched on July 17 exclusively for the PlayStation 4, earning a Metacritic score of 83 and a user score of 9.3.

No word yet on when Legends will arrive outside of the general "later this year" window.