Scattered around various dungeons and champion spawns, adventurers can find supply stones. These stones can be used to replenish various regs and bandages when needed. Try to use these for emergencies only as they are not easy to restock and the mages don't like traveling to these places to restock them to begin with. Opening a supply stone will drop a bag into your backpack with a small amount of the supplies you picked.
(Thumbnail caption: Supply stones in the New Player Dungeon.)