Just to help people find their way, here's a travel guide to get out to AC and the Ring of Fire place...
Via PoK, take the Shar Vahl Stone. You'll zone into Shadeweaver's Thicket. Head NE to Shar Vahl. Go through the city (Or use the ledges on the outside of the city wall) and zone into Hollowshade Moor. Head East until you come to a river, then head NE to the Grimling Forest zone (It's a large cave in the very NE corner of the zone). Head NW in Grimling forest to the cave entrance. There are two small platforms with several grimlings on them standing in front of the cave entrance. Once inside the cave, take your first left, then stay right, then take the middle intersection. You'll eventually come to a large chamber, the zone into AC is in the NW corner of the room.
Porting into Grimling Forest puts you rougly in the same area as the Hollowshade Moor zone is. The route is pretty much the same.
Here's a small map of AC with some labels:
Quick side note: Nothing in AC between the zone in and Ring of Fire sees invis. Totally safe.