Eight years before the
events of The King of Fighters '94, Heidern was 34 years old and was
promoted to his current rank for his proficiency in martial arts and strategy.
His promotion took place at a top-secret base in Brazil and his wife and
daughter were present for the ceremony. Before this event, Rugal
learned of Heidern's promotion and high marks. While Heidern was away, Rugal
stormed the base, killing fifty secret service officers on arrival. When Heidern
returned to base, Rugal defeated him and deprived him of his right eye, deeming
him unfit to be a part of his collection. After this, he murdered Heidern's wife
and child. Afterwards, Heidern was left disgraced and alone. He soon developed
his own fighting style and mercenary unit, the Ikari Warriors.
Since then, he
pursued Rugal to avenge his family.
Sometime before the King
of Fighters tournaments, he stumbled upon a little girl who was the last
survivor of a destroyed village. Her name was Leona
and she was suffering from severe amnesia. Heidern decided to adopt her and care
for her. He
originally forbid her to partake in any training but eventually decided it would
be good for her and the current situation. However, he refused to give Leona a
formal rank, which is his way of protecting her from some of the dangers on the
In The King of
Fighters '96, he assigns Leona to join Ralf
and Clark on the Ikari Warriors team, taking his place
while he issues orders from the sidelines. He plays a major part in the NESTS
Saga of the series, as the Ikari Warriors are on a mission to destroy the NESTS
group. Heidern researches the incidents surrounding the mysterious group Those
From the Past. When Leona experiences the Riot of the Blood after the 2003
tournament, he orders her to sit out of the next tournament so that she can
recover. After hearing Ralf and Clark's assessment of Leona, he decides to let
her enter the tournament once again. He orders them to investigate whatever role
Those from the Past and Rose
Bernstein have in the KOF XIII tournament.