Location: Travel Map -> Granemor -> Click on the Haunted House

Each stage contains 3 normal fights followed by a reward battle.
There are a total of 6 stages. And then a boss afterwards

Normal Monster List
Level 25 and Below
Baby Moglin Ghost
Evil Eye
Ghost (20)
Huge Rat
King BURP (19)
Lesser Zombie
Moglin Fire Spirit

Level 26-49
Baby Moglin Ghost
Death Witch
Ghost (20)
King BURP (39)
Kresh
Lesser Zombie
Moglin Fiend
Moglin Fire Spirit
Mummicane
Skull Swarm

Level 50+
Banshee
Demon Spectre
Fiendish Phogh
Ghost (20)
Ghost (53)
King BURP (70)
Moglin Ghost
Moglin Phantom
Mummicane
Pile o' Bones (Undead)
Shirrig
The Dreaded Hood

Reward Monster List
Level 25 and Below
Potion Treasure Chest
Rare Treasure Chest
Small Treasure Chest

Level 26-49
Potion Treasure Chest
Rare Treasure Chest
Big Treasure Chest

Level 50+
Potion Treasure Chest
Rare Treasure Chest
Huge Treasure Chest

Boss
The Reaper

BOSS DEFEATED!
You > Haunted House! w00t!

Source

Suikoman444, http://forums2.battleon.com/f/tm.asp?m=3693466