The Sword of Etheria, released in Japan as OZ (OZ -オズ- Ozu) and in Korea as Chains of Power, was developed by the same team who created Suikoden III and most of the Castlevania series of games. It was released on June 30, 2005 in Japan and on February 24, 2006 in Europe. It was also re-released as a Konami Best Hit in Japan on January 26, 2006. The game has not been released in North America.
The game's Japanese title OZ, literally means Over Zenith as shown in the opening sequence of the Japanese version. Its literal definition of "Surpassing the Peak" also explain why the words Over Zenith appears when the "Tension gauge" is maxed out. On the other hand, OZ is also used to refer to the group comprising the three greatest "Katenas" (term is used in all versions of the game).
The story sets off with Cain having visions of unexplainable things. Cain, Leon and Almira fight monsters yet it is unclear of what really is happening. Fiel ("Feel" in the Japanese version), a boy who lost his parents at an early age, grew up with his younger sister Dorothy together with their cat Toto, dwelling in a world of humans, gods and spiritual creatures called the Katenas. Trying to bring down mankind, the gods have drained the planet of 'Etheria' (its energy source) and taken control of the Katenas. Later on, a group of Katenas and monsters attacks the village Fiel is living in and kidnaps Dorothy by monsters called "Volo". Fiel then must save her with the help of two other Katenas, Almira and Leon. Thus, entering the threats present within the grasp of the gods.
In The Sword of Etheria the player controls Fiel as the protagonist where he will be partnered by Almira and Leon, who are both AI-controlled characters but each given their own individual HP gauge. The Sword of Etheria offers a new distinct battle system to the Beat 'em up genre; the player has to perform launch attacks on enemies in order to perform multi-hit aerial combos while the enemy is in thin-air as if juggling them in the air. These combos could be utilized with the aid of Almira and Leon for additional hits.
A 'Tension gauge' is shown in right part of the screen which will be indicating the player's performance with combos. It increases by chaining aerial combos and decreases if a large delay gap is present in-between attacks. In addition to this, a 'Deathblow' could be performed altogether by the party as a final blow to multiple enemies when a 'hint' displays on the screen; as a result, the accumulated points decreases. As the game progresses, the Tension gauge levels up and will be longer, thus given the ability to use more powerful Deathblows. If the gauge reaches Level 3, maxing out the gauge will display "Over Zenith" the strongest Deathblow that could be performed.
The Sword of Etheria focuses deeply in its battle system and storyline which is divided by Chapters and presents anime looking characters. Stages vary from typical forest fields, villages to different kinds of dungeons.
A special/alternate version of Chapter 9 is playable when certain requirements are met. In that chapter, the storyline will be somewhat different and the three main characters will portray some of the The Wonderful Wizard of Oz characters; Fiel as Tin Man, Almira as Scarecrow and Leon as Lion. There is also an additional unlockable story which can be played with Fiel's sister, Dorothy, as the main character.
The game also included a feature of changing the characters' costumes which could be bought in-game. These costumes were cameos from various games made by Konami which includes Suikoden III, Castlevania: Lament of Innocence and Silent Hill 3.