Corridor of Blood
Corridor of Blood (Japanese: 血の回廊, "Chi no Kairō" / lit. "Corridor of Blood") are passageways connecting several of the back-side fields of Eg-Lana. Each entryway to the corridors have a six-pointed star above it. A bar within the star shows how the corridor will connect with other fields. The orientation of the bar (the angle at which it's tilted) shows how the corridor will be tilted when you enter it, but the field to which the corridor connects is not immediately obvious from the door.
The six-pointed star arrangement above the door is a clue: the connections between the corridors can be conceptualized as if each of the fields was one of the points of a six-sided star. The bar, then, shows to which another point on the star of fields the corridor currently connects.