Rakshasa Blade

Rakshasa Blade is the sword of Ardyn Izunia in Final Fantasy XV: Episode Ardyn and its anime prologue, although he presumably also uses it as part of his Armiger in Final Fantasy XV and Final Fantasy XV: Episode Ignis. The sword is named in Episode Ardyn.

The blade is identical to the Blade of the Mystic apart from its red color, the royal arm of Somnus Lucis Caelum, the Founder King of Lucis and Ardyn's brother. The Archives describe it thusly:

Etymology and symbolism
The name is in juxtaposition to Somnus's Lucii form, although the connection is not apparent in the English localization. In Japanese Somnus's Lucii is known "the Yaksha King"; Yaksha is a class of nature-spirits, usually benevolent, who take care of the natural treasures hidden in the earth and tree roots in Hindu, Jain and Buddhist texts. The Yakshas are described in Hindu literature as the brothers of demonic beings, rakshasas.