This article contains lore taken from Warcraft III: Reign of Chaos, Warcraft III: The Frozen Throne, the manuals, and/or official bonus maps.
Adds 5 bonus damage to the attack of a Hero when carried. The Hero's attacks also become ranged when attacking air and poison enemy units for 10 seconds.
Source
These can be bought from Ancients of Wonders in Frozen Throne.