Throwing out a challenge (of pain!):
6 vs 6 doubles (strongmon)
Arena: ???
A large cavern to the south of Mossdeep city. The middle is entirely water, which goes down to very, very deep levels. On the outside of the pool is a very thin rim of rock barely above the water that stretches around the entirety of the circular arena. The BP of surf is increased by 3 and the EC reduced by 3 as well. The EC of Rain Dance is lowered by five due to a mysterious magic around the place, but it can only be used with a Damp Rock. Additionally, all other weather is banned, even with it's respective item due to the magic in the room.
DQ: 36 hours
Chills/Recovers: 5/2
Also Opening up a 4 way brawl:
3 vs 3 vs 3 vs 3
Mon type: BRT under 20 or #of moves under 25
Arena: ???
A location around Mossdeep. A mysterious white stone sits in the center of a large, circular room. Several Pokemon stand in the shadows of the edges to make sure the rock is not disturbed. If the rock is disturbed, there are five possibilities, all equally likely:
1) ???
All you need to know is that no one is likely to make it out alive. The battle ends immediately, the perpetrator getting no counters.
2) The perpetrator gets any item of his choice for the remainder of the battle.
3) The perpetrator is KO'd by a flurry of powerful attacks from the Pokemon in the shadows.
4) The perpetrator is fully restored to full energy, health, and perfect status.
5) The perpetrator gains a permanent +2 in Speed, Attack, Special Attack, Accuracy, Special Defense, Defense, and Evasion (everything that can be boosted).
The stone being disturbed is up to ref disgression. While many details are classified, the guide to the battle can assure you there will be no water source, and there will be no access to the sky or sun. Light will come from... It doesn't matter. Trust me, it'll be there.
First acceptor picks Items.
Second acceptor picks Abilities.
Third acceptor picks moves restricted.
Switch=KO and 36 hour DQ.
(Ref can go to 3 days due to complexity).
Alright, minor Mossdeep spoilers for the win. Beat me in either and I'll tell some of the background behind the arena.
EDIT: Ref gets the information too.
EDIT2: Accepting/Winning/Reffing increases chances of getting in the trial.