The player takes on the role of a summoner (known as Natial master (ネイティアル・マスター?) or just master). A master can summon spirits known as Natials. All masters and Natials have maximum HP of 10. The object of the game is to reduce the opposing master's HP to 0. The game is played on a hex grid map with different types of terrains which affect the gameplay.
- In Scenario Mode, the player must play through 30 stages, divided into 6 phases each containing 4 to 7 stages, against opposing masters.
- In Expert Mode, both the player and the enemy are equipped with all Natials and magics available in the game, but the map design is generally disadvantageous for the player. Expert Mode consists of 8 stages.
- Free Battle allows the player to configure all settings including masters, stats, Natials, magics and map. Each of human vs human, human vs CPU and CPU vs CPU are available. Secret characters are available in this mode.
There are a total of 27 masters of which 18 can be accessed normally. There are 24 Natials that can be summoned, each of which belongs to one of four attributes: Earth, Water, Fire and Heavens. Each attribute has dominance and weakness over one another in the following cycle:
- Earth >> Water >> Fire >> Heavens >> Earth, etc.
A Natial can also be day type or night type, becoming stronger in bright or dark places respectively. Summoning and maintaining a Natial requires usage of MP.
Each attribute has its own "style". For example, Earth units tend to have poor magic resistance with decent attack. They can move very well on land, while some are able to enter water terrain, albeit with penalized movement distance.
The PSP features the Trails in the Sky hidden characters in both Scenario and Expert Modes.