Battle Mountain is an optional location in Epic Battle Fantasy 4, introduced in the Steam release update (also available by purchasing the Premium Pack). It can only be reached via a new Slime Cat available in the Warp Zone - interacting with the cat teleports players to Battle Mountain.
Battle Mountain has been described by Matt Roszak as an area designed to provide extra challenge to veterans of the Epic Battle Fantasy series.
Battle Mountain is a very chaotic area, with the environment changing drastically almost every screen. As the name suggests, it is heavily populated with enemies and obstacles, many of which serve as blockades for early and mid-game players - in order to progress in the area, players must first find key items in the main game.
As a "bonus" area, the enemies in Battle Mountain do not award experience, AP, nor Gold upon defeat. However, they still drop items as normal, and they often block chests with a variety of useful items (including some unique equipment and summons). Additionally, players that visit the area early on can get some "free" scans of enemies that would normally be encountered later in the game. For instance, Armored Oak (which can be fought as early as the end of Ashwood Forest) begins its battle with a pair of Steel Fish, which players would not normally encounter until reaching the Waste Disposal Plant.
Befitting its status as an optional challenge area for experienced players, the battles in Battle Mountain are more difficult than those in other areas. Regular enemies come in massive waves (even exceeding the epic 7-wave battle against Godcat), often in combinations that exploit their individual traits and abilities. All enemies scale to the players' levels, and giant (i.e. overlevelled) foes are fairly common, giving them an evasion and accuracy bonus against the players.
However, the biggest feature of Battle Mountain is likely its selection of bosses. Not only are several classic bosses from earlier EBF games re-introduced, but the area also features "upgraded" versions of the bosses fought in the main storyline of EBF4. Deeper into the area, the party will encounter "Dark Players", evil counterparts with similar skills and abilities to them. The greatest challenge of all are the "Rushes", which pit the party against massive odds, from enormous waves of enemies to multiple bosses fought in succession, culminating in a fierce duel with all four of the Dark Players at once.