Decompiler is a 
Maliwan Shotgun
Its special effect is Tinkerer - Has a chance to fire a burst of projectiles of another element.
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How to Unlock The Legendary Decompiler Maliwan Shotgun
Weapons
Legendary Loot
Overview
How To Unlock
Unlock Location:
- Progress through the (FL4K And The Last Resort) DLC until reaching the Boss
Blackgrin
Farm Method:
- Defeat Blackgrin to get a chance at the Decompiler.
- After use the Encore Machine nearby to reset the fight.
- Repeatedly defeat Blackgrin until the Decompiler drops.