Hadel:
The Reliquary of the Giants is where the Giant heroes are buried. In the times of the Giants, when a hero died, their soul would be embedded within the Scroll of Afterlife while their body was put into the ground. This was done so that the power of Giants would be passed on from generation to generation.
I won't stop you from visiting the Reliquary of the Giants if you wish to pay your respects to them.