Jiggig is a place where dead Ogres were buried until they started to come back to life as undead, Zogre and Skogre. Ogres built a barricade to stop these undeads from escaping. Jiggig can only be entered during and after the Zogre Flesh Eaters quest. According to Grish, it is named Jiggig as it's where Ogres jig.
Undead ogres may disease a player. This can be countered with Relicym's balm. They are also very resistant to normal weapons, but Brutal arrows work on them very well.
There are many ogre coffins scattered about Jiggig. They can be opened either with an ogre coffin key, which is a drop from zogres and skogres, or by picking the locks through the Thieving skill.
The entrance to Jiggig is guarded by several Ogres. Uglug Nar is a shaman who will sell the player supplies useful for fighting in Jiggig, although many of his items are not in stock by default. Grish is another shaman who starts the Zogre Flesh Eaters quest. Pilg and Grug are wounded ogres who have been injured while fending off the undead ogres. There are also two uninjured ogre guards. The first guards the barricade which blocks the way into Jiggig itself, and will let the player in during the Zogre Flesh Eaters quest. The second guards the only three ogre coffins that are outside the barricade, and will throw the player into Jiggig if they fail to steal from the coffins.