I dont know how to get to the Obelisk rubbing while the fang boss is located at the opening of the 3 locks.
You have to complete the entire dungeon (3 minor bosses and 3 puzzles) and then do the Dungeon's Major Boss. Behind the battle circle for the last of the four bosses is where you wish to go.
Note: sometimes you can sneak around the final boss for the rubbing.
Note 2: The Vault is on the main quest line and most people just wait till they get there for the quest you are mentioning.
To get the Vault of Ice Obelisk rubbing, you must enter the Vault of Ice and complete the dungeon. The Obelisk is in the fourth room at the end of the dungeon.
If you have the quest for the Obelisk rubbing, but not for the Vault of Ice dungeon itself, you will have to wait until you follow the storyline and get the Vault of Ice quest. Then you can do both at the same time.
Or else you can teleport to a friend who already has the Vault of Ice quest (to get the Obelisk rubbing).
