Now, I didn't say that Iskandar would go to the trouble of actually getting the Stone back, did I? All he has to do is convince the clerics that he will, and after his plans are accomplished...
Long Knives aren't copyrighted by the Romans, after all.
Now I have this image of the clerics demanding Iskander get the Stone back afterwards and the Shah denying it ala the Monty Python Argument skit.
"You said you would get back the Stone if we agreed to support you!"
"No I didn't"
"Yes you did!"