Hi prsm...
Mmh, i have some idea, but not pretty sure if its ok.
I saw some monster like yellow slime, will take a dropped item.
How about you make some special item that can obtainable
during the event only, and after the event the item will dissapear from anyone who still hold it..
This special item, lets just say it like, "pink pencil", "red pencil" and "green pencil", this item will droped at some cave that already set up by GM, where the cave full of monster like "Yellow slime"(who will take every dropped item).
After all of the dropped special item disappear, cause of the yellow slime, then contestant will be allowed entering the cave, and hunt down the yellow to get the special item.
There is rule for more interesting, example:
-Contestant have to collect 5 green pencil, 2 red pencil and also 1 pink pencil, to get the real prize from GM..
-contestant have to be naked or unarmed and also using Brawling skill during to find the special item (this just example, coz i think its very few ppl used this skill, and also if GM can check the skill were used on contestant) hehehe....
-after the collected item are enough for prerequist item, the contestant have to race to find a gm who hold the real prize for the event, my suggestion the GM have to be hide somewhere in the place that have some sort of aggressive monster, so if the contestant not carefull enough, they will start over to find gm at soul menhir....hehehe...
This could be hard, contestant have to found quick the GM at dangerous area that have some agressive monster, and at that moment the contestant using brawling skill, if they want to change the skill, contestant will only wasting time...
-for the contestant who found gm first, they will granted the real prize (lets say, who ever sit first up the GM won it....hehehe...
But yes, if i calculate this could be hard to make it, you need at least 3 or 4 GM during the event (1 hide, 1 dropped item, 1 guard the cave yellow slime, and
Another GM watching area and invisible to all player)
But maybe you could customized my idea prsm...

This is just an idea for me and i think this should be very fun...hehehe...
Im sorry for my bad english here....
Cheers.
Ichimaru Leon