I have defeated all 3 bosses and "interacted" with the oblesik in the correct order-and I "hear a lock break" but when I go to the dungeon to get in-there is still a lock on the door-what am I missing?
Each boss has a puzzle that is only unlocked after you've defeated them. So, bear this in mind and attempt the dungeon again. Once all puzzles are solved and obviously all bosses are defeated, the final door will unlock exposing the final boss.
You are invited into the Vault 2 different times. 1st time you're instructed to talk to Shalek then pointed to the big door right across from him. 2nd time DON'T TALK TO HIM!!! Run by him and go all the way to the back and left. In each instance you have to solve a riddle in order for that door to open. Win that battle and move on to the next. Riddle and Battle 3 times. After you've solved and won three times the big door across from Shalek should open. THEN you do the rubbing from the obelisk.