Multiplayer mode is included in Dungeons and Dragons: Dark Alliance. You can play with your friends through Online Multiplayer and soon through Split-Screen Couch Co-Op play.
Dungeons and Dragons: Dark Alliance Multiplayer
Local co-op will not be available for D&D: Dark Alliance at release. But, according to the developers it will be included in a free DLC at summer 2022.
Online multiplayer will be allowed wherein different players from across the world will join in a four-team party. You can even use the same hero in the party!
Dark Alliance allows cross-gen play, meaning PS4 and PS5 users can play with each other as well as Xbox One and Xbox Series X. The same goes for PC.
There's still no information on if cross-platform play will be available for all platforms. But according to Xbox News, it is available between PC (Windows 10) and Xbox consoles.