Ah Da was not a person from Diminishing Moon City. He was a person whom Zheng Weilong had rescued back from the brink of death when she was younger. He was very skilled, but he almost died under the pursuit of his enemies.
In the Upper Realm where relationships between humans were fragile and weak, it was rare to meet someone like like Ah Da who valued morality. He started to follow by Zheng Weilong's side after he managed to survive to repay her life-saving grace. He stayed by her side and protected the weak her who had no spirit power. Before Zheng Weilong became an adult, Ah Da had lost count of the number of assassination attempts he had fended off from her 'brothers and sisters.
In terms of strength, if compared with Ruan Zhongshan, Ah Da's ability to condense spirit inscriptions was similar, but in terms of stealth, Ah Da prevailed.
Ah Da immediately told Zheng Weilong everything he heard in the City Lord's manor.