The subject of this article originates from non-canonical sources. To find out about what is considered "canon" see LOTR:Canon.
The Shade of the Wolf was a demonic ghost of a Werewolf that either the Witch-king of Angmar or one of his sorcerers could summon during Angmar's war against Arnor. The ghost's power was ice related. It had the power to summon normal Wolves to attack enemies, freeze enemies, eat enemies and was a very fast being. The werewolf's origins are unknown and it is questionable how the Witch-king or any of his sorcerers could summon it since the Witch-king and the Sorcerers of Angmar, despite being very powerful, were still Men.
The Shade of the Wolf is a level 25 power for the Angmar faction in The Lord of the Rings: The Battle for Middle-earth II: The Rise of the Witch-king.