Chaotic theory: Khilai created the Decompositon mugic to defeat Pheren'tal in the first M'arrillian invasion.
When Khilai was the last creature in Perim who wasn't mind controlled by the M'arrillians, She plan on cutting the M'arrillians off their mind controlled by stealing Pheren'tal's power she got from the Khilaian sphere. She created the callstones to stored the Khilaian sphere's power in.
In her haste to stop the M'marrillians and save Perim, she never occurred to her if the mugic has any side effects. When Khilai used decomposition on Pheren'tal, the m'marrillans were slowly losing their control over the creatures. However, this cause Pheren'tal not only losing the power of the sphere, but her abilities as well. This lead her to probably to her death.
Khilai than used Pheren'tal's callstone was used to create the doors of the Deep mine to prevent the m'marillans from breaking down the door and the keys was well.
Than Khilai created the sanctum in case what happened with the m'marillans was to never happen again.
















