Ruby Eye Blade (Japanese: 魔王剣ルビーアイ・ブレード, Kanji translation: Demon King Blade, Romaji: rubīai burēdo) is an offensive black magic spell which calls upon the power of the ma-ō Ruby Eye Shabranigdu. The spell has two methods of casting. The first is similar to Astral Vine in many aspects, but stronger: It can enchant an otherwise ordinary blade, which gains a red aura and the ability to cut through almost anything, high-ranking mazoku included. The second method, on the other hand, is closer to the effects of Ragna Blade, creating a sword made entirely of red light without the need of any material focus. It is said that the spell's power is equivalent to that of the Sword of Light, although this seems to be mere speculation, considering the Ruby Eye Blade was introduced in the novels at a tim