Poison Spiders are a bit stronger than regular Spiders in that they hit harder and can poison you with venom a little stronger than that of a snake. Giant Spiders will summon up to two poison spiders to break your shielding and enable much stronger hits. It is not advisable to attack one below level 4.
Location:
Found in various caves and plains around Tibia (Including Rookgaard).
Strategy:
Losing one or two hit point per turn due to poison is not worth using exana pox. Just steadily eat food to counter the poison, even if you are in Rookgaard.