Acala Vidyaraja is believed to be an incorporation of the ancient Indian fire deity Agni into Buddhism. Agni was integrated into Buddhism, simultaneously revered as the Heavenly Fire and as Acala Vidyaraja. It is said to offer benefits of purification from impurities and enhancement of financial fortune. It is believed to possess the power to transform a baby in its mother's womb into a male child, making it widely worshipped by samurai seeking male heirs during the Warring States period. Typically depicted with three eyes on one face and four arms holding a sword, noose, vajra, and staff, engulfed in flames, Acala's appearance varies, with depictions featuring two eyes, two or six arms, and diverse attributes.
Residing in the realm of "Kasho Zanmai," between the human realm and the Buddhist world, Acala resides within a world of flames, burning and purifying human desires to prevent their spread to the Buddhist realm. This attributes to its virtue of purifying by burning away impurities, leading it to be worshipped by people as a deity that cleanses places like toilets and kitchens. This practice originated from the belief that toilets were pathways for vengeful spirits, aiming to purify these spirits. Even today, Acala Vidyaraja's amulets can be found in restrooms of traditional shops and temples. Notably, within the Tendai school of Buddhism, Acala Vidyaraja is considered one of the Five Great Wisdom Kings, taking the place of Vajravarahi.