Baldur's Gate Wiki

Gargantuan Spiders are the largest of the various species of Giant Spider. They are, in essence, the same to Giant Spiders as as Giant Spiders are to Huge Spiders. A not-so straightforward upgrade, however; these spiders possess two special abilities in Siege of Dragonspear: Web Tangle (inflicts paralysis for 2 rounds on a failed save vs breath with a -2 penalty) and an on-hit effect for their melee attacks that inflicts sleep for 5 rounds on a failed save vs death with a penalty of -2. Like all of the monstrous spiders, they are immune to the effects of Web.