Battle of Kingdom combines real-time combat with the presentation of a board game. You are tasked with defending your kingdom from invaders over the course of six stages, each of which contains several battles to complete. Most battles are mandatory to complete and backtracking is not possible, but most stages have a branching path, giving players a degree of choice in their approach. Not all spaces on the stage board involve battles – some spaces will give the player another chance to buy monsters, and others will present the player with a choice between three chests that can provide a random amount of points, a free monster, or nothing at all.
Using a starting pool of 800 points, as well as any points earned from winning battles and occasional events, you must select from 16 different monsters to form your team for battle. Each monster has different stats, such as HP, attack, and speed, and each monster also has a unique ability that can be used in battle. The goal is to eliminate all of the opponent's monsters while keeping yours alive.
Combat takes place between you and the opponent. You have five commands to choose from during battle: moving, attacking, using your monster's ability (which costs 30 points per use), healing yourself (in exchange for 20 points), and a push that sends the opponent back towards their starting point at the cost of 50 points. When attacking, you can press the A button to spend 2 points to have your attack come out faster, or press B and spend 5 points to do a jumping attack instead. Commands are selected by moving a cursor over them at the bottom of the screen.
A password is provided after every battle, allowing players to continue where they left off or revert to a previous part of the game. If you're defeated in battle, you'll be brought back to the title screen and must enter a password or start the game over.