Coalescipede

Spiders are found within the Shaded Citadel. In most cases, spiders are afraid of you and will run away from the slugcat. Within Shaded Citadel, nests of spiders are dangerous. Spider behaviour changes when there are large amounts, causing them to attach to each other, become hostile, and attack slugcat. Sometimes, spiders can be encountered outside their nest in a centipede-like formation. However, they only do this when they feel threatened, or if slugcat comes too close. Avoiding them can decrease the chances of a spider-pede formation. These critters can be broken apart using a spear, or scared away by throwing the purple balls seen growing in Shaded Citadel. Currently, the effectiveness of firecracker plants is unknown. They appear to fear light, such as the light emanating from lightstones. Lightstones can be traded from scavenger merchants or stolen.

Trivia

 * The number of spiders needed to kill you depends on their size: 3 when large, 6 to 7 when medium.
 * Tiny spiders aren't harmful.
 * Scavengers in the Shaded Citadel have lightstones with them. This appearss to indicate that they are aware that spiders fear bright light.
 * A spider-pede formation will snatch lanternmice from slugcat.