Seige of Ba Sing Se
The Five Wisdoms
Bumi was not born a Prince of Omashu, instead being the illegitimate son of King Inda IV and a court jester. In his youth he was a friend of Avatar Aang before the latter's disappearance. His trademark eccentric behavior developed during this time, often playing pranks on his family. However he would unexpectedly become heir apparent the year after the Air Nomad Genocide, as his legitimate brother Inda was killed as part of the Delegation of Reckoning, forcing Bumi to become the new heir.
Bumi would prove himself a powerful bender, helping give Fire Lord Sozin his first major defeat at Mu Bay, holding the landing off long enough with a combination of Earth Bending and interpretive dance for the Southern Fleet to destroy the Fire Lord’s fleet. This victory would ensure that for nearly the entire war, the Southern Earth Kingdom would remain free of occupation. Shortly thereafter Inda IV died in his sleep, and Bumi donned the crown of Omashu. Which he replaced with some antlers because “it looked way cooler.”
Bumi’s role in the early stages of the war was largely limited to supplying the vast armies of the North From the relatively secure south, and keeping the south inline. Many Kings of Omashu would have taken the opportunity to either declare independence from Ba Sing Se, or even allied with the Fire Lord to get even with their old rivals. But Bumi would hear none of it, famously ordering the construction of a mail chute from his throne room to the dungeons so that any defeatist advisors could be swiftly imprisoned.
The Rise of Azulon saw new challenges for Bumi. Omashu was forced to watch helplessly as her stalwart ally the Southern Water Tribe, was slowly dismembered by the Fire Nation. With the retreat South of the Tribesmen, the Fire Navy earned free reign over the seas, exposing much of the Earth Kingdom to raiding. Here Bumi’s diplomacy shone through. Despite his occasionally odd tactics (asking for “honest opinions of my hair” as tribute, trading gum for rock candy) the King of Omashu forged a powerful coalition in the south, bankrolled by rich families such as the Beifongs. Bumi stands out as one of the few Earth Kingdom leaders to have genuinely friendly relations with the sandbenders, whom he called “the only sane people on the planet” and “surprisingly good at cooking sunfishwhale, what with living in the desert and all”.
Bumi initially had good relations with the Earth Kings, sending support and men to aid in their desperate battles for control of the North. However as the Zheng Dynasty declined relations deteriorated. Newer kings feared Bumi’s Earth Bending skill, and thought he coveted the throne. To be fair, some did whisper that Bumi was the only king worth the name, particularly as the Fire Nation crept closer to Ba Sing Se. Bumi spurned all such talk, dutifully sending his tribute, although he did not help matters by sending pranks “in the hopes that I can get the Dai Li to laugh.”
The late stages of the War saw Bumi forced again to face combat personally, although he no longer could face armies alone. The Fire Nation broke out of the colonies and swamped the Earth Kingdom. The regency of King Kuei essentially ended any central direction of the war effort, and the Earth Kingdom fractured badly. Bumi played little role in the Defense of Ba Sing Se, although his presence on the Fire Nation’s Southern Flank did divert some troops from Iroh’s campaign.
Bumi was now the only person alive who remembered the war’s beginning.
Bumi would briefly host the Avatar on his way to the North Pole, then would face the Army of the Great Divide as it marched South on Omashu. Controversially he would surrender the city and himself without a fight, fearing mass casualties from an urban fight. He would spend his time imprisoned needling his captors with bad jokes. When the time came they were either so endeared that they surrendered without a flight or fled in terror.
However the Omashu Army was nonetheless able to withdraw in good order, and supplied many of the forces used on the Day of Black Sun. That same day, Bumi was able to escape his confinement and single handedly evict the Fire Nation from his city. He called it "a nice bit of exercise" and "very fun." This action seriously disrupted Fire Nation supply lines and prevented a total occupation of the South.
Bumi made his way North, likely via his contacts in the Order of the White Lotus, and joined the Order outside of Ba Sing Se. There he played a key role in the reconquest of the city, backing the renthronement of Kuei.
There is some dispute about whether Bumi used spiritual means to extend his life or whether he was just really old. When asked he replied "why not both?" And then laughed far too much. In any event, his health began to fade after the end of the war. He found time to become a great patron of Metalbending, infamously disguising himself as a child to get into the first classes offered by Toph Beifong.
Bumi never married ("I'm a king, if I want some cake I can get some cake without all the the trouble of getting married") and so obviously there was significant concern over who would succeed him. To put these fears to rest he organized a city wide scavenger hunt to select an heir, which was won by a cobbler named Mochee. Bumi would spend his last few years training Mochee in the arts of Earth Bending, ruling, and pie throwing.
King Bumi of Omashu would die aged 121 in 109, after the longest reign of any known monarch. His funeral was attended by all the world leaders, who got to witness a funeral procession designed by Bumi himself. There were bad puns, good puns, sing a longs and heartfelt goodbyes. And at the end everyone got a gift bag filled with rock candy.