If a magic item allows you to cast a spell it is clearly marked MAGIC ITEM and SPELL. Such items can be carried by any character, including heroes as well as wizards, unless the card itself indicates some specific limitation.

Spell magic items function exactly like other spell cards. During the magic phase the character can cast the spell once when it is the player's turn to do so. A spell bound within a magic item requires no power cards to make it work, but will probably be bound by some other limitation. For example, it may be that it can only be cast a limited number of times, or its power might give out on a specified dice roll. See the cards themselves for details.

A spell cast from a magic item can be dispelled, destroyed, rebounded, etc, just like any other spell. The main advantage of these magic items is that they can usually be carried by any character model, and so broaden the spell casting ability of your army.