The Aching Roil is a Legendary 
Ripper SMG which is obtainable through the How Rush Saved Mercenary Day Vault Card.
Its unique effect prevents it from firing when it Overheats, but swapping gun modes reduces heat.
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How to Unlock the Legendary Aching Roil SMG
Legendary Loot
Weapons
Overview
How To Get
Unlock Location + Farm Method:
- Acquire the How Rush Saved Mercenary Day Bounty Pack (this is free!)
- Complete daily and weekly challenges for Vault Card Tickets
- Daily Challenges provide 3-4 tickets, Weeklies provide 10
- Exchange 10 tickets for a choice of Aching Roil, Extolled Rooker, Missilaser, or Hardpoint!
- You may purchase these guns an unlimited number of times to roll different stats and attachments.
Vex
Phase Phamiliar
C4SH
Cleromancy
Incarnate