Steamheart Shotgun

Steamheart Shotgun is a superior-quality equipment item that drops from Eclipso in Challenge Mode. Once equipped, it unlocks the Heavy-Barreled Sniper Rifle weapon style.

Source
The Steamheart Shotgun is an item drop from Eclipso, found within the Challenge Mode version of the Lair of the Spectre.

Dropped item

 * Eclipso

Style unlock
Upon equipping the Steamheart Shotgun, a character unlocks the Heavy-Barreled Sniper Rifle weapon style, which can be accessed at any time from the Style Window.


 * Heavy-Barreled Sniper Rifle