The goblin dungeon is mainly used for quests. During the Dwarf Cannon quest, you rescue a dwarf child from the goblins, then in the One Small Favour quest, you battle a Slagilith. Unless you wish to kill goblins, there is not much of a use for this dungeon.

You can only receive the privilege to fight Slagilith during One Small Favour. After you defeat him, you can not try to conjure him again and therefore cannot be used for training.

Near Saglith, there is a small crack that you can enter. You will find the level 160 ghostly Bouncer that is killed to receive the Shadow Sword.

Dungeon Rat (Level 12) Giant Bat (Level 27) Goblins (Level 2, 5, 13) Slagilith (Level 92)