Crossfire is an open source, cooperative multiplayer graphical RPG and adventure game Crossfire is an open source, cooperative multiplayer graphical RPG and adventure game. Since its initial release, Crossfire has grown to encompass over 150 monsters, about 3000 maps to explore, an elaborate magic system, 12 races, 15 character classes, a system of skills, and many artifacts and treasures. Crossfire is based in a medieval fantasy world and is similar to other games of this genre.