There is only one location of any spires in Mons Letalis. That is in the south-west central area of the zone. The area is marked with a pink square on my map. Initially, climbing will not get you where you need to be. You must use the cave-like entrance and then climb the stone stairs. Be prepared to be assaulted on the way and again when you reach the platform at the top of the top of the stairs
Rising from the corners of the platform are four spires. You will want the one on the north-west corner. And again, climbing the spire will not work; instead see a tilted, broken column. Climb that, then proceed to climb the spire. At the flat top you will see four white-flame lights. Click anywhere and a container opens. Insert the turquoise gem that is half of what once was the Globe of Discordant Energy. That item then becomes a translucent light blue gem.