A substance known as the "black fog" is swallowing the entire kingdom, first a forest and a lake, then a village. No one who has entered this fog has ever returned. Now princess Katia's kingdom is being threatened, and using the rune stone and mystical cards that turn into monsters, she must find a way to eliminate the black fog.
Cards are a significant factor in the gameplay. When played, cards transform into various beasts.
There are 3 different card types: "weapon" type cards will appear briefly for a single attack but can be summoned more than once, "independent" type which makes a monster appear on the field which fights for Katia until it dies and "summon" type which are somewhat like weapon cards but cause a lot more damage to enemies (or heal Katia).
Each creature is associated with one of 5 elements, with each element (other than neutral) having a weakness and strength (e.g. fire beats wood but loses to water).