If you want to play Elden Ring Nightreign in a duo, the Seamless Co-op mod is already out, dead simple to use, and it won't mess up your vanilla save

A bird man character from Elden Ring reads a book in a library.

FromSoftware is apparently reserving the right to add an official two-player mode to Elden Ring Nightreign⁠—right now you can only play solo or in a trio. But Yui, the modder behind the Seamless Co-op series of Souls multiplayer hacks, has already done it again with Elden Ring Nightreign a mere day after launch.

PCG senior editor Wes Fenlon and I hopped in for a round, and it works exactly like you hope it would⁠—it's even slightly more buttoned up than the already-great original Seamless Co-op, won't mess up your game by drawing Easy Anticheat's Eye of Sauron, and even opens up Nightreign for further modding.