Blackas Shadow Prince is a supporting character in The Demon Sword Master of Excalibur Academy. He serves as one of the two last loyal servants, along with Shary, to the series' protagonist, Leonis Death Magnus, the former Dark Lord known as the Undead King. His background reveals that he is the prince of the Realm of Shadows and has been a longtime comrade and friend to Leonis. In the past, Blackas was the one who persuaded Leonis not to take part in a great war, arguing that Leonis was the last remaining Dark Lord, which ultimately led to Leonis deciding to seal himself away in the Great Mausoleum for a thousand years.

In terms of physical appearance, Blackas initially appears to be a large black dog, but his true nature is that of a royal wolf. He has yellow eyes and black fur. His personality is defined by deep loyalty and a tendency to offer wise advice, particularly to Leonis, whom he serves faithfully. As a longtime friend, he is one of the few beings who can speak candidly with the Dark Lord.

Blackas Shadow Prince plays a significant role in the story as a companion and ally to the reincarnated Leonis. Their relationship is one of mutual trust and cooperation, as the two work together effectively in combat and share crucial information. He is also notable for his developing bond with the character Sakuya Sieglinde, who renames him Kurogane Fluffymaru, a name he openly dislikes. Despite this, he accepts the food she gives him, and the two eventually form an interesting bond. This relationship represents a key development for Blackas, as he adapts to the new era and forms connections beyond his ancient allegiance to Leonis.

Regarding his notable abilities, Blackas possesses the power of speech and can use his heightened senses, particularly his nose, to detect the presence of the Voids, the primary antagonistic creatures in the series, as well as other enemies.