KUALA LUMPUR (Reuters) -Malaysia's Sultan Ibrahim from the southern state of Johor was installed as the country's 17th king on Wednesday, taking the oath of office in a ceremony at the national palace in Kuala Lumpur. The monarchy plays a mostly ceremonial role in Malaysia, but its influence has grown in recent years, prompting the king to wield rarely-used discretionary powers to quell political instability. Under a unique system of monarchy, the heads of Malaysia's nine royal families take turns to be the King, known as the "Yang di-Pertuan Agong" every five years.