Monsters are killed to obtain XP and loot. There's a 1/5 (20%) chance of encountering a rare monster in any areas.
Magnus's Combat guide now on wiki aswell! dont miss out on all the good information Combat Guide
Fields
Regular Monsters
Rare monsters
Forest
Regular Monsters
Rare monsters
Caves
Regular Monsters
Rare monsters
Volcano
Regular Monsters
Rare monsters
Northern Fields
Regular Monsters
Rare monsters
Haunted Mansion
Regular Monsters
Grandma File:SkeletonMageIcon.png
Rare Monsters
Moon
Regular Monsters
Rare Monsters
to be continued..
Other Monsters
Faradox Guardians
to be continued..
Special Monsters
Quest Monsters
Tank 
(only available during the Tank(boss) Quest)
Ent Boss 
(only available during the Ent(Boss) Quest)
Thief Leader 
(only available during the Thieves Leader Quest)
Ghost Miner 
(only available during the The Ghost Miner Quest)