A Thunderbloom bulb.
This article contains lore taken from Warcraft III: Reign of Chaos, Warcraft III: The Frozen Throne, the manuals, and/or official bonus maps.
Thunderbloom is an exotic plant well known for its unstable and dangerous properties.
Chen Stormstout asked Rexxar to retrieve a sprig of thunderbloom as one of the ingredients for his brew.[1]