The only significant plants in the outdoors area are a few green stain cups and clouded funnel caps slightly to the west. It is possible that there may be a bandit or two in the area around the ruins.
Arpenia is a showcase for every Ayleid trap there is. Despite its size, it's quite deserted, with only rats and mudcrabs scattered around. There are a few Ayleid chests and casks from which to procure loot. Most of the casks contain leveled jewelry, coins, or potions, and there are no enchanted weapons to be found inside any of them.