Cloud School was an organization established before the first Battle of Divine Will, their members were of different races such as Humans and Demons.
Their goal was to unravel the mysteries of the world and uncovering the secrets of the ancient ruins
According to legends, when most human beings were still ignorant, some sages came together to fan the flames of civilization. They taught people how to make ironwork, weave clothes, and tillage livestock until human beings populated the entire Land of Dawn.
Hundreds of years later, they reached the summit of their power. All those in power sought to win them over by any means, and many members then turned from becoming knowledgeable communicators to being the private collection of those in power.
The leader of the sages discovered this point and moved the organization out to major city-states. He also stipulated that they should not be easily involved in politics, urging them to only focus on the mysteries of the world and uncovering the secrets of the ancient ruins. Since they were relocated to the top of a mountain covered by clouds all year round, everyone called it the Cloud School.
Although these people rarely interacted with the common people, their status was still elevated. No matter how the kings in power kept changing, they were still respectful to the Cloud School. Every year, they would send a large number of supplies and young students, just to get guidance from these sages.
But this period did not last long as the demons soon infiltrated mankind. The first Battle of Divine Will broke out... It was at this time that a disturbing rumor gradually spread. It stated that these brutal and terrifying beasts were introduced into the Land of Dawn by a sage hundreds of years ago.
The reputation of the Cloud School plummeted, and it was taken over by the demons as no leader was willing to lend a helping hand. Finally, it became a dusty memory of history books.
The members of the Cloud School held suspicions on the Battle of Divine Will, but their position and theory created conflicts with their races leader, such as Heathtalese and the current king of Demons.
They warned their respectives races, but couldn't turn the tide of the war.
Since the demon in the school can become a grand lord, then it would have been normal for witches or normal people from the higher-ups to come from the school. 
Samantha may have been a member, with her social position, and her time period correspond with the existence of Cloud School.
The first Battle of Divine Will declared the end of the Cloud School as their races were confronting each others.
The Three Chiefs destroyed all records—a past where they coexisted with demons would make people hopeful, especially when the situation is bad, it would only eat away at humans' determination to resist, so the Cloud School must be forgotten as an undesired blemish
The disbanded Cloud School is at most a cherished memory to people now, and when the outbreak of the second Battle of Divine Will comes, even this memory will cease to exist. That period of their history is not recorded in any scripts.
With Heathtalese's death, the Cloud School on the demon side lost its protector.
Valkries visited the mountain where the school used to be situated every 100 years and would stay at the ruins of the school building for a couple of days every time she went there.