A bit less than 800 units if Essence just to use a Secret Art... Not even Khal was stupid enough to use such an ability that cost that much.
'No, I must have done something wrong. Logan told me this Art will be tricky to use, but he never mentioned it will have a huge Essence consumption.' Khal suddenly realized a problem and began to use his brain to come up with a solution.
And soon, he indeed found an issue. It was about the number of jade markings he placed around the City. It seemed every carving was fueled from his Essence, and the more there were the more of his Essence was needed.
However, he couldn't decrease the number of his markings, as one jade mark had a hundred-meter radius and had to be inside another carving's radius to work. Thus, if he wanted to inspect everything inside Moon City, this 100 was a must and he couldn't decree the amount.