Spider

Spiders are common enemies. They are found on most floors, including The Binding of Isaac: Antibirth's new floors.

Fissure
Fissures behave similarly movement-wise to Trites, jumping erratically towards Isaac and around the room. However, when they jump, they release a small amount of red shots that go towards Isaac. Occasionally, they will stop jumping and stand still in order to spew a large burst of red shots.

Soi Creep
Soi Creeps are a variant of Wall Creeps. Like Wall Creeps, they stick to walls, attempting to line up with Isaac. It will then fire a long stream of white shots in a straight line, as a reference to the item Soy Milk.

Strider
Striders are a type of spider that can only spawn in Downpour. They glide on the water towards Isaac in short bursts, and can swim across gaps.

They seem to be normal Spiders that can travel the watery surfaces of Downpour, as they replace most normal Spiders in Downpour, and have an almost identical appearance.

Rock Spider
Rock Spiders are a type of spider that behave very similarly to normal Spiders. They crawl towards Isaac in short bursts if he's near. They also turn into normal Spiders upon death.

If they touch fireplaces, fire projectiles from enemies like Fireworms, or fire pillars from enemies like Dragonflies, they will turn into Coal Spiders.

Dannies can spawn Rock Spiders alongside their rock projectiles.

Tinted Rock Spider
Tinted Rock Spiders spawn in place of a Soul Heart when a Tinted Rock is destroyed in the Mines. They behave almost identically to normal Rock Spiders but are slightly faster. Upon death, they will spawn a Soul Heart. If frozen by icicles, they will not spawn a soul heart.

Coal Spider
Coal Spiders are spawned when normal Rock Spiders touch fire. They have more health than regular Rock Spiders, and upon death, the coal persists and can continue to hurt Isaac.

The coal left behind upon their death will burn out and disappear after a while, and if all enemies in the room are dead, the coal will disappear automatically.

Coal Boys can spawn Coal Spiders.

Trivia

 * If a shopkeeper in the Downpour is blown up, Striders will spawn instead of the usual Spiders.
 * In Repentance, there is an enemy called Fissure, however it is more of a Host-like monster.