Nouda was a spirit (and by all accounts a particularly powerful one) who existed in that undefined class of beings that exceeded the power of even marids (the most powerful type of commonly summoned spirits). Like Ramuthra and Uraziel, Nouda was a spirit that was rarely summoned to earth or even given classification thanks to his extreme power. According to Bartimaeus, he was "not sympathetically inclined".
To lesser spirits, he was referred to as "Lord" Nouda.
He was presumably destroyed by the spirits trapped in Gladstone's Staff, with the help of the iron from the great glass palace.
Nouda is known to have been summoned by some of the most tyrannous and powerful leaders through history, usually with incredibly disatrous results.
Darius of the Persian Empire had his own army annihilated by the demon, destroying the city of Persepolis in the meantime.
Moctezuma II of the Aztec Empire was another similar master. Through a slight irregularity in his summoning technique, Nouda burst from his restraints and destroyed most of Tenochtitlan, allowing the Spanish to overrun the Aztec's capitol.
Nouda was also employed by the Assyrians for the battle of Nineveh. Bartimaeus claims he devoured 1000 Medes during the battle.
Timur the Cruel used him to sack the city of Dehli, where the spirit built a 50 foot high pile of the heads of prisoners.