Portal of Morth is a competitive board game inspired by tower defense video games. During the game, the players have a team of heroes with which they will fight against an ever increasing amount of powerful enemies. As a general rule, the game has a duration of five rounds, with one wave per player each round. Each wave is divided in four phases:

1. Lord Morth's phase: The starting player rolls the enemy dice into the portal board to determine in which path the enemies enter the boards. To do this, the player rolls as many enemy dice as indicated on the turn track, and a 12-sided die to determine the exact position of the portal. Also, the players receive cards to trump their opponent's strategies.

2. Portal phase: The players may pay gold to turn the portal, modifying the initial enemy distribution. In turn order, each player may pay as much gold as they want to move the portal in any direction. Once all players have moved the portal or have passed their turn, they take the enemy dice that ended the phase in their zones of the portal board, placing them in the corresponding paths.

3. Heroes' phase: Players move and attack with their team of characters, trying to eliminate all threats from their boards.

4. Assault phase: Enemies advance, trying to exit the player's boards. The starting player rolls a three-sided die, and each player has to add the resulting number to the initial movement value of each enemy. If an enemy escapes a player's board, the player takes damage.

Once all rounds are finished, the game ends and the player who has the fewest damage points wins!