Appears to refer to 'magic' or 'powers' that may be conjured by some men. Also refers to a 'glass like' object, possibly quartz crystals that represent these powers.
The graph displays the other subjects mentioned on the same pages as the subject “Krugalung”. If the same subject occurs on a page with “Krugalung” more than once, it appears closer to “Krugalung” on the graph, and is colored in a darker shade. The closer a subject is to the center, the more "related" the subjects are.