Hi to everyone. I'm hoping I can get some help with this part of the game.

I have ADKs walkthrough but I haven't been able to summon Ankthar or find the obelisk that opens the treasure room. I can the passageway by the hero monument but it is gated. It's the only part of this map that I haven't been able to do - after having torn most of my hair out in frustration (;-) ), any chance anyone can help? If not, is there any way I can progress to the next part without going into the treaure room - every exit I have found is gated.