Regulus

Sai Ralog Baal's "Pawn" is a highly compelling character who ascends to a high-class devil in Volume 4 of the Shin series. While he usually appears as a masked boy, behind this façade lies Regulus, the Sacred Gear known as the "Regulus Nemea, the Lion King's Battle Axe." Regulus is a God-killing tool who continues to operate on his own even after his master has died, rampaging until all enemies in sight are annihilated. It is a fateful development that, through Sai Ralog Baal's actions, this Sacred Gear was reincarnated as a devil.

When he enters Balance Breaker, Regulus transforms into the armor "Lion King's Firm Hide" for Sai Ralog Baal, which is another intriguing aspect. Although Regulus's original form as a Sacred Gear is a battle axe, in Rating Games, he can transform into a massive golden lion with a gem on his forehead — a truly impressive sight. While Regulus is immensely powerful even on his own, there is always the risk of losing control and going berserk. That is why a combination with Sai Ralog Baal, the only one capable of restraining him, is absolutely essential. The dynamic between these two adds great depth to the story and captivates the audience. The bond between Sai Ralog Baal and Regulus perfectly embodies the appeal of the anime.