Summoning Quarhodron: where to find his tomb
The fastest way to find the Tomb of Quarhodron is teleporting from the ruins to the Valley. The area is where we find the Hermit.
With the teleport platform behind you, turn left and go forward until you have passed the small rock bridge (figure 1). At some point, on your left, you will see a hidden narrow road going up the mountain (figure 2).
Go up this road and in front of you there will be a small rock house. Behind that, you will see the entrance to the tomb: it is guarded by a Troll and some Goblins (figure 3).
Enter the tomb, you'll have to read the tablet that Myxir gave you for the summoning. This way, Quarhodron will appear to you.
In order to obtain the tablet to open the Temple of Adanos, you'll need to answer the questions of Quarhodron.
Let me know in the comments if you found the road to the tomb of Quarhodron!