Black Recluse

Black Recluses are hardmode enemies that spawn in Spider Nests, but can rarely be found in the Cavern layer. It can inflict the Venom debuff and itself is immune to the Poisoned and Venom debuffs.

Farming
If you can find a large enough Spider Nest you can make a hole in the top and use a piercing weapon, such as the Poison Staff or Nimbus Rod to take advantage of their fast spawn rate. Poison Staffs sell for about (and with a good reforge up to ) making a great early hardmode farming strategy that gets you souls and money. It can also be turned into an automatic farm with some traps from the Lihzahrd. Another good way, is to get a Shadowbeam Staff, make a 1 block hole in a side of the nest, and shoot the beam into it. This is also helpful, because the beam can break the Cobwebs and illuminate the nest.

Trivia
The name "Black Recluse" is a combination of the spider names "black widow" and "brown recluse"; both spiders are commonly known for their venomous capabilities. This is reflected in the monster's appearance and in its drops.