The Smoke Weaver is a rare weapon that is great for Rogues in Last Epoch. If you want one for your character, there are thankfully several ways to find one in the game.
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As with many items in this isometric ARPG, there are a few different ways to obtain one of these daggers. One of the ways is to farm it from Reign of Dragons' echo rewards. Echo rewards can be used to farm specific items from echoes across the Timeline, guaranteeing a specific type of reward. In order to have a chance at getting a Smoke Weaver, you'll need to get the "Unique or Set Sword or Dagger" echo reward. There are several other swords and daggers that can drop from Reign of Dragons, but this will at least allow you to narrow it down to a weapon type, making it much more likely that you'll get the specific item you're looking for.
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Another way to get a Smoke Weaver for your Rogue is to use the Runes of Ascendance on another dagger, gambling on the possibility of getting the Smoke Weaver out of it. You have about a 7.69% chance of getting a Smoke Weaver when using a Rune of Ascendance, according to the Last Epoch Ascendance calculator found here.