The Giant Spider is the 2nd boss in the game, and is found in Haggerdom, in the 'The Silken Wildwood' stage. It is a melee boss.
High Jump - The boss will leap into the air, and land upon a random character, making them its new target.
Call of the Forest - The boss will summon 4-5 small, weak spiders which enter from either side of the screen to attack the characters.
Web - The boss will wrap a random character in a web, preventing movement and auto-casting/attacking. They can, however, still use any abilities.
This boss fight is a fairly simple one. Use your other damage dealing classes to take out the summoned spiders, and keep your tanking character (not necessarily a tank, Rogues are actually best) attacking the boss. When it uses High Jump, simply attack it again with the tanking character to regain aggro and continue fighting. The 'Web' ability is more of an inconvinience than anything else, and doesn't really pose a threat unless you were already in a pinch and it targets your Cleric/Tanking character.