In Esoteric Buddhism, a Wisdom King (Sanskrit विद्याराज Vidyārāja, Chinese Míngwáng 明王, Japanese 明王 myō-ō) is the third type of deity after Buddhas and Bodhisattvas. The Sanskrit name literally translates as "knowledge king", thus the Chinese character "明", meaning knowledgeable (and/or bright) is used, leading to wide array of alternative English names including Radiant King, among others like Guardian King, etc. Wisdom Kings belong to the Buddhist Pantheon. In Tibetan Buddhism, they are known as Heruka.
The female counterparts of Wisdom Kings are known as Wisdom Queens (Ch: Míngfēi 明妃; Jp: 明妃 myōhi), although the distinction is often ignored. (Wikipedia)
Five Wisdom Kings
Front left is a protective deity: the Heavenly King Zocho, and back left another one: Heavenly King Komoku.
Image source: en.wikipedia.org
Five Wisdom Kings
The Five Wisdom Kings is the most important grouping of Wisdom Kings (Vidyaraja) in Esoteric Buddhism. They are wrathful manifestations of The Five Wisdom Buddhas.
Image source: commons.wikimedia.org
#1: Acala (alternatively, Achala or Acalanatha in Sanskrit, Fudo Myoo in Japan)
Image source: en.wikipedia.org
#3: Kundali (Gundari Myoo) is one of the five major Wisdom Kings in Buddhism.
Image source: en.wikipedia.org
#8: Kujaku Myoo (Mahamayuri), Tokyo National Museum
Image source: ja.wikipedia.org