To play Descent in coop has been a unsatisfied dream since I was a kid; I was wondering if it is possible to play with Overload. I gave a quick look to the menus and I only see "Anarchy" and "Team Anarchy", perhaps it is not possible to play coop?

There is no coop.

Mike Kulas wrote on the Steam Forums: “There are no specific plans. We would love to add it, but it's a lot of work. We'll have to wait and see.”

Source: https://steamcommunity.com/app/448850/discussions/0/2592234299530923734/