Vadam is a Sangheili state in Yermo, Iruiru, Sanghelios. It was named after its founder Ther 'Vadam, the ancestor of the Vadam family. The bloodlines that control the state share the surname Vadam, which is customary for Sangheili naming.
The state of Vadam was named after Ther 'Vadam who was said to have been imprisoned by his enemies. He was starved in the prison and yet refused to kill himself. He eventually became so thin from hunger that he was able to slip his body through the bars of his window. Even in his weak state he managed to scale the cliffs of Vadam keep, and swim down the river that surrounded the keep and also provided a good source of energy. He had to walk many days and he had to eat vermin and scraps to keep himself alive.
He soon came across the vast desert that was in the interior of the Sangheili land. He started rebuilding his strength and toughness in the years to come, and managed to make allies with other wanderers. His newfound allies had statuses that were lower than Vadam's but they were willing to fight under Vadam's leadership. Now that he had warriors under his command he returned to Vadam keep. He successfully defeated those who had imprisoned and laughed at him.
 Sangheili civil war
In March 2553, Sangheili insurgents led by the Servants of Abiding Truth launched assault on the state of Vadam. Along with nine ships and forces from Nuan Keep and Rtova Keep, Avu Med 'Telcam commanded the assault from the frigate Unflinching Resolve. Eventually, however, the Unflinching Resolve suffered a direct hit and crash landed. Despite being caught off-guard it appeared as though the Arbiter would be victorious, however, news spread that he allowed humans to land on Sanghelios; this caused many keeps to ally with the Servants of Abiding Truth and the tide turned in their favor. The Arbiter was caught off guard as his own reinforcements couldn't arrive on time, and he reluctantly accepted Admiral Terrence Hood's offer for help in fending off the attackers. The UNSC Infinity destroyed the rebel forces with a MAC round, leaving a large crater near the Vadam coast and effectively ended the attack.
 Areas in the state of Vadam
The tale of Ther 'Vadam may be a biblical allusion, as the bible states that a man called Moses escaped from Egypt with the freed Jewish people, before traveling a massive sea and wandering for 40 years in the desert. If this is indeed a biblical allusion, then the escape of Moses could be related to Ther's own escape; the sea could be related to the river Ther had to cross, and the desert could be related to the 40 year long trek.