Item
Mage's Staff
Unique
Effect
If this item is held by a 
Mage, double its stats.
Where it drops
No drop source recorded in the game files.
Other Unique items
Questions people ask
What does Mage's Staff give in Guildrun?
If this item is held by a Mage, double its stats.
How many items can a hero hold?
Three at ranks C, B and A, and four at rank S. Specializations and relics can push that higher, up to a hard cap of six. The Executive alone adds two.
Can I equip the same item twice?
Yes. Doubling up is legal and is used in real builds. The Rush Duelists build on the tier list runs two Vanguard's Bracelets on Rip.