Megami Tensei Gaiden: Last Bible (女神転生外伝 ラストバイブル?) (Revelations: The Demon Slayer in North America) was developed by Multimedia Intelligence Transfer and published by Atlus and is part of the Megami Tensei series. The game originally was released in Japan in 1992. On March 19, 1999, the game was remade with updated graphics for the Game Boy Color. This version would be localized for North America and released on August 27, 1999. Also, Sega released an identically-titled port of the game for the Game Gear. This is not to be confused with the sequel released exclusively on the Game Gear and titled Megami Tensei Gaiden: Last Bible Special.
Megami Tensei Gaiden: Last Bible is a side-game (gaiden) of the Megami Tensei universe. The humans in this game can call on the power of Gaia. The main hero, El, learns the art of Gaia and must save the world from an evil Gaia master (called Gaia Meisters in the original Japanese version), assisted by his friends Kishe and Uranus. The world in which this game takes place is a borderline-prehistoric world with many towns being named after mythological or ancient cities such as Atlantis and Harappa. This is unlike the other Megami Tensei games, which are set in modern or a futuristic Japan.
In a review for the game on IGN, Adam Cleveland awarded the game a 7 out of 10, noting that "Although it's not perfect for everyone, it should appeal to those of us who are constantly keeping our eyes open for hand-held journies [sic] with tons of battles based on choosing from menus." Revelations currently holds a 76.67% on GameRankings.
Source: Wikipedia, "Revelations: The Demon Slayer", available under the CC-BY-SA License.