It was the seat of government of the New Mandalorians and the personal residence of Duchess Satine Kryze. There was a throne room, discus sion room, dining hall, and an office for Prime Minister Almec. During his visit to Mandalore, Obi-Wan Kenobi went to see the Duchess at the palace, where he confronted Almec. Satine and Padmé Amidala later ate and had a discussion about corruption on Mandalore. Also, this was the place where Ahsoka "turned in" the four traitorous cadets to find Satine.
Around 20 BBY, the Death Watch, with the aid of the Sith Lords Darth Maul, Savage Opress and their Shadow Collective, conquered Mandalore from the Duchess and the New Mandalorians. Pre Vizsla - the Death Watch leader - betrayed the two Sith and had them imprisoned. After they broke out, Maul challenged Vizsla to a duel in the throne room, which saw Vizsla killed. In addition, it saw Maul absorb the Death Watch into his organization, prompting Bo-Katan and her Night Owls to flee.
Sometime later during the battle that engulfed Sundari, the Dark Lord of the Sith Darth Sidious entered the throne room where he confronted the two brothers. Igniting two lightsabers, he challenged them to a duel. In that duel, Sidious was strained only once, but gained the upper hand after impaling Opress and subjecting Maul to Force Lightning.