To support a ruler of this kingdom defending a siege, Calixtus III began the practice of the ringing of the Noon Bell. A ruler of this kingdom (15[1])used the ouroboros and crusader imagery when founding the Order of the Dragon. After receiving other (-5[1])titles, that ruler of this kingdom organized the election of Pope Martin V at the Council (15[1])of Constance. A ruler of this kingdom hired the standing (*) “Black Army” of mercenaries and amassed the (10[1])largest (10[1])library outside of Italy, which was later brought to Istanbul (10[1])after his 1490 death. Matthias Corvinus and John Hunyadi ruled this (10[1])kingdom, which fought the Ottomans at battles like Varna before being decisively defeated in 1526 at Mohács [moe-hatch]. For 10 points, name this kingdom founded by the Árpád dynasty that became the main eastern part of the Habsburg realm. ■END■