Calvaria's Star
A halo deployed in the stratosphere, blazing with focused sunlight.

A reflector created with magecraft. The 50km long, 10km wide blade of light beaming towards the surface can be compared to an aurora possessing mass, or a guillotine of light. It is High Thaumaturgy that Ciel came up with after defeating the Ancestor who was her sword mentor; apparently she uses his Idea Blood to initiate it.

After firing at full power against Arcueid the remaining magical energy was used to launch one last shot, and it was this move that turned the tables in the endgame.

Tsukihime Material I - Calvaria's Star