Explore the desert. The guide stones look a bit different here: they’re yellow obelisks. Click on them all and take note of the information on them.
On the north side of the desert you will find a locked gate that you need to open. To do this, first find the bone chest in the northwest and destroy it with your army. Once destroyed, a bronze staff will have appeared by each of the guide stones. The image on each staff will relate to the god mentioned on the guide stone. The staff you found by the bone chest symbolizes Seth.
Now go to the big temple in the middle of the desert. If you click on the different parts of the temple, it will tell you which of the gods can be worshipped there. Around the temple you will find metal circles, one for each god/part of the temple. The staffs you’ve found need to go into the circles. If you place a wrong staff, they will all return to where you found them.