Conqueror Rune

The Conqueror Rune (支配の紋章, Shihai no Monshou, Control Rune), also known as the Black Rune (ブラックルーン, Burakku Rūn) is a rune that grants its bearer control over monsters while simultaneously weakening their resolve.

Suikoden
The Conqueror rune is a rune that gives its users control over monsters, but simultaneously weakens their willpower. The Conqueror rune can affect the user so long as it remains attached to their body; however, the user will break free of the rune's control should the rune melt and all effects caused by the rune will vanish. The melting of the rune can be painful and illicit a burning feeling. When bearers break free of the rune, they may not remember what happened to them during the time they were under the rune's control.

The Conqueror rune was utilized by Windy in an attempt to control Kwanda Rosman, Milich Oppenheimer and Barbarosa Rugner. Save Barbarosa Rugner, who was unaffected by the Conqueror rune due to his Sovereign rune, the Conqueror rune affected both Kwanda Rosman and Milich Oppenheimer during the Gate Rune War. Kwanda Rosman used the power of the rune in order to drive the Kobolds of Kobold Village insane, but the curse was broken by the melting of Kwanda's rune.

Trivia

 * The Conqueror Rune is the only known rune that can melt.