When players first collect Eridian weapons in the original Borderlands they are incredibly difficult to use. Although Eridian weapons have unlimited ammo that regenerates over time, these weapons can only be fired a limited amount of times before needing to recharge. Leveling up Borderlands’ Eridian weapon proficiency will allow Eridian weapons to be fired more times before running out of charges, and it will also improve their recharge rate, and their overall performance.