The boss of Stonefang Tunnel.
A giant, red-eyed spider which can shoot webbing and use amped up versions of the spells fireball and ignite.
Little is known about the Armor Spider, the spell descriptions from its Demon Soul give no clue on its origins, leading to speculation. There are no other spiders seen in Stonefang so the boss is not likely a corruption of wildlife native to the mine. No mention of a large spider is made by characters or the Stonefang archstones indicating it is not a creature of folklore like the Storm King or Adjudicator. The only other reference to spiders in the game is the spiderstone which is coincidentally only found in Stonefang Tunnel. Spiderstone is "fabric-like" and "transparent," indicating that the ore source is the Armor Spider's webbing after it has gone through some manner of process, perhaps super-heated by the spider's flame attacks.
Armor Spider's Hard demon soul can be used to craft smaller scale versions of its fire attacks, ignite and fire spray. It can also be used to create a bow in the shape of the spider's leg which imbues the arrows with fire damage.