Hiya,
The Crown of Tempest is actually classified as a head-item - but vendor drops cannot be enchanted. The idea is to give an incentive to go through dungeons and kill bosses; both Casper and Frigus have very good drops, so if you are bored, why not organize a group with a tank and healer, and go kill those bosses? XD
Items may be enchantable with several spirit bottles at some point, but at the moment it's one spirit bottle per item for balancing reasons. Especially for spirit bottles that give 3% dodge, multiple enchantments would quickly break the game balance. ;P
