Hunting in this game is a bit strange...

[Skyly HUmar]

Ive been trying to find a soul eater for a while now but IDK how drops work in this game.

Do things drop in their specific field at any time or only when the picture of the item is up on the quest selection? And do things drop from specific monsters or from the firld itself?

[ForgottenReality]

The pictures of items at the quest counter are items you can get. However, there is no guarantee it would drop. Those items, as far as I can see, drop from any enemy in the field. The items you can get changes periodically. For example, Soul Eater may drop in Hard mode Free-Field Desert mission, but later it changes to being dropped in Hard Mode Rare Ore Excavation mission (last Desert mission). Hope this helps ^_^