My partner just pointed out to me that what might have you confused is the duplicate object rules. You can't have the same object (enchantment, equipment, conjuration, or creature) attached to the same thing multiple times, but you can certainly have multiple copies affecting the same thing. For example, [mwcard=MWSTX1CKJ01]Enchanter's Wardstone[/mwcard] is attached to a zone, and thus you can't have more than one in the same zone (also prevented by the zone exclusive trait in addition to the duplicate object rules) but it's effect is arena wide and you could have multiple wardstones protecting your enchantments. 3 wardstones, in different zones, would make it cost six extra mana for each enchantment your opponent wanted to destroy.
Note: creatures don't really count here because they aren't attached to anything. I just included them because they are objects and I didn't want to inadvertently cause added confusion by leaving them out of my list of objects.