A Storm Cloak is a fantastic item, found in Ultima VI. While wearing it, all magic in the area is negated, essentially crippling magic-strong foes like dragons and daemons, making it almost too easy to beat them. However, the drawback of this wondrous cloak is that if used too often, its negation ability will run out, and the cloak will vanish.
Only three Storm Cloaks were found in Ultima VI. The first one was given to the Avatar by Jaana in Yew. She kept it in her house and gladly gave it to the Avatar, after joining the party, to help. The second Storm Cloak was in the treasure of Hawkins, and Homer demanded it as payment for giving the Avatar detailed instructions on how to find it. The Avatar agreed to the deal. The last cloak could be found on the body of an unfortunate adventurer in the Swamp Cave.