"Run!"
The moment Su Yu and his team started their offence against the gang from the Yu Long Palace, Daozi, the protector and a group of True Monarchs of the Nascent Soul Realm from Li Huo Hall felt their scalps tingle. Without a second thought, they immediately steered their warship and tried their best to escape from the location.
While Su Yu returned to the battlefield outside the Fourth Immortal City, he and his allies dedicated approximately half a quarter of an hour, managed to capture the group of True Monarchs from Yu Long Palace, which included the two Nascent Soul Peak Protectors.
Among the over forty True Monarchs of the Nascent Soul Realm from Yu Long Palace, more than thirty had fallen while Su Yu and his team captured the remainder alive.
As for the inhabitants of the Earth Immortal Mansion, they were all only slightly injured, with none having fallen.
As for why they aren't killing the rest....
That's because they are worth more alive.