Gaia no Monshō (also known as the 'Crest of Gaia') is a fantasy round-based strategy game by NCS and conversion of a game originally released for the NEC PC-8801 in 1987. Gaia no Monshō is a turn-based strategy game at heart - the player moves troops around a battlefield and attacks nearby enemy units. An Auto Battle mode is also available and gives the option to let the AI figure out of the player's next move. The game offers several play modes - the first one (Scenario Mode) gives the player the chance to jump straight into battle using predefined troops. The second (Construction Mode) allows him to build his own army using unit points. The last one (Campaign Mode) conveys story plot elements and starts in the siege town of Dirl, where king Sieghart battles the fierce Böser. This mode requires more complex strategy and the player must assemble his own troops using unit points and units lost in battle don't come back during the campaign. Unlike the other two modes, it offers a password system to save the player's progress through the game.

The Light and Dark forces are engaged in a fierce war and Böser, leader of the Dark Army, is now ready to capture the Rall Tower, source of the world's energy. Sieghart, leader of the Light army, is the only one who stands between the evil Böser and the complete decimation of the kingdom.