It'll also help you bag a SIVA cluster.
Before we proceed, there's a prerequisite. You have to have completed the Wrath of the Machine raid. Once you've done this, you'll receive an Isenfyre token.
Take the token to the main fire pit at the Iron Temple and you'll be shot up into the air, landing on top of the tower where the SIVA cluster is. You may remember this cluster from the King of the Mountain story. Depending on your viewpoint, this is either the easier or hardest way to reach it.
The fun really begins once you drop off the other side of the tower. You can go exploring, and better yet, open up the doors to the Iron Temple so that other Guardians can join you for a stroll around the mountain.