A whirling storm of scarlet-banded spiders scuttles toward you.
Scarlet Spider Swarm CR 2
The bite of a scarlet spider is extremely painful. A creature bitten takes a -1 circumstance penalty on attack rolls, weapon damage rolls, and ability and skill checks until cured. A neutralize poison or remove disease spell, or a DC 13 Heal check removes the penalty. The check DC is Constitution-based and includes a +2 racial bonus.
Environment temperate forests
Organization solitary, pack (2-4), or colony (5-10)
Scarlet spiders dwell in temperate forests and make their homes in the hollows of trees, under fall trees, and in dense foliage.
Scarlet spiders are deadly, aggressive black spiders about 3 inches long. Their legs are long, thin, and covered in a thin layer of dark hair. Their bodies are solid black with horizontal bands of scarlet ringing them. Scarlet spiders are not web-spinning spiders; therefore, they do not possess the standard web ability of other spiders.
Scarlet Spider Swarm from the Tome of Horrors Complete, Copyright 2011, Necromancer Games, Inc., published and distributed by Frog God Games; Author Scott Greene.