Boss Rush Mode

Boss Rush Mode was an unused game mode that didn't make it into the final version of Mother Russia Bleeds, with the only material available for it is a locked cover featuring the faces of several different bosses, with Nekro being the most recognizable among the faces of what appears to be the Warden, a Gimp, and a Bouncer.

Description
As it's name obviously implies, Boss Rush Mode was going to be a battle against all the bosses of Mother Russia Bleeds one after the other, it is unknown if there was going to be a new arena, new arenas, or if the original arenas for each boss were to be reused as the player is transported between them, and it is unknown if this mode is ever going to be implemented in a future update.