Black Recluse

Black Recluses take over spider nests once Hardmode begins and wander a short way out into the surrounding caverns. On older console versions and the 3DS they replace Wall Creepers there completely; on current versions the creepers still turn up occasionally alongside them. The name is black widow and brown recluse folded together, two real spiders known for their venom, which tells you what this one does before you meet it.

Contact has a chance to leave Acid Venom on you, a slow bleed stacked on top of a hit that already landed hard, and in early Hardmode that combination kills characters whose owners thought they had enough health. It is also black, on a dark web covered wall, in a dim nest, so the first hit frequently arrives with no warning at all. Light the place properly or drink a Hunter Potion before going in. From Expert upward it gains a ranged web spit that applies Webbed and pins you in place while everything else in the nest closes the distance. That attack runs on a cooldown which pauses whenever it loses sight of you or has no clear line, and which gets pushed back every time you damage it, so staying aggressive genuinely keeps it quiet. On For the Worthy and Zenith worlds those web shots also scatter real cobwebs across a patch of ground wherever they land, which walls you into the fight you were trying to leave.

Low health and high defense. That pairing punishes fast weak hits and rewards single heavy strikes, so a slow hard hitting weapon outperforms a rapid one with the same listed damage by a wide margin. Knockback is the other answer, since anything that shoves them keeps them off you long enough to finish the job. A yoyo is the comfortable option because it works at a distance and holds them back while it grinds. And like every spider in the game, they cannot climb a vertical shaft two tiles wide, so a narrow drop shaft doubles as a safe firing position.

Once your gear has moved past them, a spider nest turns into a decent income source. The coins they carry are the small part of it. The real value sits in the Poison Staff and in banking Spider Fangs toward Queen Spider Staffs, both of which are worth several times the loose change when averaged across a session. Nests are compact and enclosed, so a small cleared arena near the middle of one keeps the whole place feeding you.