Boss: Buru the Spider(s)
Located in Nest of Greed
Best training areas:
Doomy Forest-1
Strategy: Not a bad room to train in because all the monsters are on the same level. Just dash from left to right and back again to get the monsters closer together. Then start attacking them.
Doomy Forest-2 & 3
Strategy: Same as the first room, these just have more monsters. You can just ignore the monsters at the top.
Inharu Swamp-3
Strategy: Same as above. (Best room to train in in my opinion)
Inharu Swamp-2
Strategy: An okay room, just might take time to get all the monsters together.