Jonos Arryn

In the year 37 after the Conquest, barely after Aenys I Targaryen's coronation, Jonos Arryn locked up his own brother Ronnel, Lord of the Vale and loyal to the new king's cause, and proclaimed himself King of Mountain and Vale.

Aenys ordered his Hand, Lord Alyn Stokeworth, to gather a fleet and an army to march on the Vale, but withdrew the order for fear of leaving King's Landing undefended while Harren the Red remained in rebellion.

With no word from the king, Lord Allard Royce took the initiative and marched against the rebels, besieging the Eyrie and closing off any escape for Jonos.

Cornered, Jonos killed his brother Ronnel by throwing him through the Moon Door, an act that earned him the nickname the Kinslayer.

Prince Maegor Targaryen arrived at the Eyrie riding Balerion, and the mere sight of the dragon was enough for the fortress garrison to seize Jonos and hand him over to Lord Royce.

Jonos ended up thrown through the same Moon Door through which he had killed his brother. Surrender spared his followers from burning, but not from the noose: Maegor ordered them all hanged, denying the highborn among them the privilege of beheading.