Kingdom Under Fire: Circle of Doom is an Action RPG video game developed by Blueside and published by Microsoft Game Studios exclusively for the Xbox 360. It is the fourth installment in the Kingdom Under Fire series and the first released for the seventh generation of consoles. Chronologically the game's story follows Kingdom Under Fire: The Crusaders released in 2004 and its prequel Kingdom Under Fire: Heroes released in 2005. It was first released in Australia on December 5, 2007, followed by Japan on December 13, 2007 then later in North America on January 8, 2008 and in Europe on February 1, 2008.
Unlike the previous Kingdom Under Fire games in the series, Circle of Doom's gameplay is significantly different, with the real-time strategy elements completely absent, with much of the gameplay focus being on the role-playing and hack and slash combat aspect.
Unlike the previous instalments in the Kingdom Under Fire series, Circle of Doom is entirely a hack and slash role-play, much is the vein of dungeon crawlers and focuses entirely on the player’s chosen character out of five (sixth can be unlocked), thus lacking the real-time strategy formula of the previous games. Given the single character focus, much of the gameplay revolves around close quarter combat with multiple AI controlled opponents throughout each level. As the player progresses with each kill, they gain experience that eventually leads to gaining a level, the maximum being level 120. Each time the player levels up they receive a given number of experience points to boost their overall health, skill points and luck. Higher-level players will also be able to wield better weapons and armour and allow more options for magic use. Levels are also generated at random, with differing paths and amount of foes between each (while foes are still confined to certain areas) and destructible environments with the use of heavier weapons.
While the player has a standard health bar, the skill points forms another (SP bar) that when the player performs an attack or uses magic, their SP becomes depleted and recovers when nothing is performed, so the player will be unable to attack if there isn’t enough SP at that moment of use. The more SP and the faster rate it can recover allow longer chains of attacks. The Luck skill determines the quantity and quality of loot and gold dropped by slain foes. The Luck skill can also help in the game’s "synthesis" system, one which lets players pay gold combine items to improve one, for example combing a powerful weapon with a weaker one will result in its overall attack power being somewhere in between, with enchantments from both also present. Luck improves the chances of a successful synthesis along with a larger investment of gold.
Items can also be bought and sold when the player encounters an Idol in each level that serves as buyers and sellers of various items. There are three different Idols in total; Death, Love and Greed who excel more in certain items than others who appear at certain times of the in game’s "moon phases". The Idol also provides a safe sanctuary where foes cannot enter, thus allowing players to "sleep". When the player sleeps, they appear in the dream world where they interact with other characters who progress the story by providing quests, insight and allowing players to learn new skills, most usually requiring a certain number of particular foes to be killed. Magic and weapons can assigned to 4 commands buttons on the Xbox 360 controller at any given time, X and A buttons for use of weapons/attack and B and the right trigger for use of magic. Potions that can quickly boost health and SP or cure magic affects inflicted by enemies can be applied to the left and right bumper buttons. The player also has Accessory slots where armour and stat increasing jewellery are applied for effect, more being available for purchase from Idols. The game features three difficulty levels; Normal, Hard and Extreme that differ between the strength of foes, but however only Normal can be played to begin with and the other difficulties are unlocked by completing Normal (then Hard for Extreme mode) and are only playable with the character that unlocked them.
Circle of Doom also allows up to four players to play through each level and corresponding boss fights over Xbox Live.This can allow joining players to play through levels they have yet to progress to as long as the host has. Players that receive items and experience online will still reap the benefit for their character offline at the same time, thus allowing players to trade items and complete quests with others but foes toughness increases the more players there are. The Xbox Live headset is also supported for use.