"Hahahah! A Guardian? Here? Now? You're a bit late, fool. CluDathoon has already activated the Camlann Device here, and completely scorched the surface of the entire planet. During all the chaos, Xanthar and I managed to escape Avalon's prison, and finally take back what is RIGHTFULLY ours. Now that Xanthar is Avalon's new Emperor, you should speak with him, at the Throne."
Fly across the gap in the bridge and walk up to the main archway. Take the path to the right of the market, next to Satele's Clinic, and follow it up the steps and across the bridge to the throne room. Walk inside and speak with Xanthar.