Below is a suggestion by Spoiler. Stated they are having an issue publishing and asked me to publish. Share your thoughts and opinions.
-That the heads of fire cave leave the weekend on the map, it can be at a random time and a random place
-When the boss appears, leave a message telling the players that the boss is in the world
-You can leave Chief Red on Saturday and Chief Blue on Sunday, each one giving a different experience and a different loot.
-Anyone who hurts him will receive the experience and that it is not necessarily to be in a group and receive the EXP, Drop that he releases such as jewels or items nvl 90.
-The boss is difficult to increase life and damage so that players do not abuse the event and force players to kill the boss in a group.