The Poison Staff is a spell that shoots four poison fangs in the direction of use. The fangs spread out randomly in a narrow angle and fly in straight lines for an indefinite distance, given that their trajectory is not interrupted by a solid block. One of the four will always traverse the position of the cursor at the time of use while the other fangs will fly above or below. The poison fangs will pierce through enemies and inflict the Poisoned debuff on them.
Due to the fact that the Poison Staff is quite easily obtained, it is a good weapon for early hardmode, and can be used to kill bosses quite easily, especially with full Spectre Armor equipped.
Like with most magical weapons, the best possible prefix for the Poison Staff is Mythical.
With the right gear equipped, the Poison Staff can do about 100 base damage, and 200 with critical hits. Combining this with its spread and piercing abilities makes the Poison Staff great for large waves of mobs, including the Goblin Army and the Pirate Invasion.
The poison staff seems to be a spider head on a stick.