Reach and solve the 3 Astrariums in the Hinterlands:
Peraquialis in Dead Ram Grove
Judex in The Outskirts
Draconis in Hafter's Woods
When all 3 Astrariums are completed, the location of a cave will be revealed. The cave is actually an otherwise inaccessible section of the cave explored for the Apostates in Witchwood quest. It contains a chest with a Snake BladeSnake BladeRare Dagger Requires: Level 9
Damage: 69–71 +2% Attack +14% Critical Damage Bonus On hit: 5% chance to apply poison.
For location of the Astrariums see the three icons on the map; the cave is located approximately around the blue star.