The Toxic Razorknife is a Pre-Hardmode weapon that acts like a Harpoon but the projectile isn't connected to a chain and you can shoot more that one projectile at a time. It can be Purchased from the Knight for 10 Gold.
While it is a great weapon, the projectiles have a larger hit box than it’s counterpart, the Vampire Knives. This makes it hard to shoot in areas with low ceilings, downward from a ledge, or in very confined spaces.