Divide the class into groups and assign each group a flashcard on the blackboard. You can either draw or prepare the monsters (I found pictures on Irasutoya and printed + laminated them because you need multiple monsters). 

Place or draw the first monster on the board. Assign the monster health points (I recommend keeping it under or just above 10 so more groups have a chance to win points) and secret points (I used number flashcards and put it face down on the blackboard. The teacher sets a timer and calls the target English. Students repeat the teacher.

When the timer sounds, the last called flashcard indicates the group that gets to attack the monster. Either the teacher or a student volunteer from the group rolls a die. Subtract the number from the monster’s health points. If the monster’s health reaches 0, the monster is defeated. The secret points are revealed and awarded to the group that defeated the monster. The next monster is brought out.

The game continues as such until either all monsters have been defeated or time has run out. Group with the most points at the end of the game is the winning group!