Heidern is a character in The King of Fighters series who debuted as a playable character in The King of Fighters '94 in the Brazil Team (later known as the Ikari Team), along with Ralf Jones and Clark Still. Heidern is the commander of the Ikari Warriors, and issues orders to his adopted daughter Leona and his best soldiers: Clark Still, Whip, and Ralf Jones. He is also known as the General of the Soldiers of Fortune.

Eight years prior to The King of Fighters '94 tournament, a 34 year old Heidern was just promoted to his current rank for his exceptional proficiency in martial arts and strategy. The event took place at a top-secret base in Brazil and his wife and daughter were present for the ceremony. Rugal Bernstein, who caught wind of Heidern's high marks, stormed the base when he was away and killed fifty secret service officers on his arrival. When Heidern hurried back from his duties, Rugal deprived him of his right eye and deemed him unfit to be a part of his collection. Instead, he murdered Heidern's wife and child. Disgraced and alone, he developed his own fighting style and mercenary unit, the Ikari Warriors. Since then, he pursued Rugal to avenge his loved ones' deaths.

Sometime before the King of Fighters tournaments, he found Leona as the last survivor of a destroyed village. The girl was amnesiac and Heidern adopted her to care for her. He originally forbid her to partake in any training yet became lenient due to her inclinations on the matter. His refusal to give her a formal rank is his way of protecting her from some of the dangers on the battlefield.

(Source: SNK Wiki)