Add War of Emperium (WoE)
As seen on Ragnarok Online, the war of emperium is a guild-fight for the control of the castle by destroying the main artifact or crystal (the Emperium) in a determined period of time (30 mins).
To access the third floor, where the emperium remains, you need to destroy another two crystals located into the second floor, so the portals may open. The castle is also guarded by other other monsters/traps to make a little more difficult the entrance to the third floor and to the emperium room.
This idea has been implemented into other tibia servers with relative success, as the winner guild sees slightly improved its rates (in this case loot/exp/catch?) in 50%, or any other reward that you may find appropriate.
This war needs coordination and strategy within the guild members in order to achieve the control of the castle. Any loss or death inside the castle does not count and are teleported outside the castle (pvp zone). When the Emperium is destroyed, the guild whose member made the final blow becomes the controller and everyone that is not a guild member of the controlling guild is automatically teleported outside the castle. Now the controller guild is able to use the special statues inside the castle to get immidiate access to the third floor and its leaders are able to use the "!recall" command to teleport 8 of its guildmates who are not currently at the WoE next to him.
This could be finally a good idea to improve the utility of guilds other than asking for pokemon prices or eventually helping in any quest, and to leave behind the big failure of the war system that no one uses right now.
Here is a video from a brazilian OT Server that explains the mechanism and a video of a WoE of mTibia (I would be happy to cooperate as well if you need to, I played a lot of WoEs in mTibia):
youtube.com/watch?v=Fe8gtnBAujk
youtube.com/watch?v=dYH0Quwxw-U