Hint: PMB HQ: Once the Arena opens,
choose "Monster Massacre" from the list of options.
At the start of the battle use the Decoy Knack to lure all the
slimes in your direction.
Then, have someone cast a
level 1 area damage spell (for example, Blizzard).
It should kill them all before anyone else gets to attack them.
You can get twelve items if you kill all of the slimes.
The items all increase your stats; for example, the Life Apple
which raises strength, the Wisdom Apple that raises intelligence,
and another item that raises dexterity. It costs 3,000
to enter each time.