Gate Rune

The Gate Rune (門の紋章, Mon no Monshou), also rendered as the Rune of the Gate, is one of the 27 True Runes. It is the rune of both Leknaat and Windy, having been split between the duo sometime prior.

Suikoden
The Gate Rune was safeguarded by the Clan of the Gate and when that clan was destroyed, the rune was used by Windy and Leknaat to escape the massacre. Leknaat considered the Gate Rune to hold terrible power.

The rune is, in fact, two runes, the "front" and "back" (also called the "entrance" and "exit") runes. The rune was split between the two clan sister with Leknaat bearing the "back" rune and Windy the "front." Their powers are considered to be connected in some fashion.

Combined with the power of the 108 Stars, the Gate Rune was used to bring Gremio back from the dead, although Leknaat stated this to be a unique event. The Rune of the Gate could also return monsters to the nether world although, like all runes, it is nullified completely by the Sovereign Rune.