IN THIS EXAMPLE I'VE USED "Sotetseg" as the boss but that would obviously be changed to suit the server.
For example, you join a "Lobby" or "Waiting Room" for the boss, when joining you can choose either "Attacker" role or "Helper" role, when there's ATLEAST 2 but max 3 of both roles in the waiting room (cant have more than 3 attackers and cant have more than 3 helpers) you go into the boss, the the helpers have to fish for food, cut down logs & and cook food to stock a chest for the "Attackers" since they are not allowed to bring supplies into the fight but overloads. (so the fight should take a bit) and at certain HP percentages the boss will spawn some sort of NPC that is directed towards the "Attackers", which the "Helpers" have to freeze and kill the npcs with ice barrage (brings a use for the ancient magiks) or they do immense damage to the "Attackers".
138 Combat - Attackers
99 Fishing/Cooking/Woodcutting/Firemaking - Helpers (Gives more of a use to grind skills for pvm)
Make the "Helper" able to bring Barrage Runes, A hatchet & tinderbox
Make the "Attacker" unable to bring anything but armour & overloads (So they have to rely on the helpers for the food so theres no afking)