The monsters that spawn during Code 66 are categorized as a One Hit Monsters. They will remain on the Kingdom Map for 2 hours and 55 minutes, or until they are killed. They can be killed with only 1 Hero, 1 Energy, 1 Hit and will drop 1 Loot item. Any hero in any level can be used for hunting them.
Killing One Hit Monsters will not give Guild Gifts, but they do drop large amounts of resources when hit.
Normal monsters may fail to spawn at the exact spawn times, when One Hit monsters are spawning simultaneously. Killing the One Hit monsters will improve the spawn rate of the Normal monsters.