It didn't take Arthur a long time to finish testing the six new recruits and if he were to rank them then the strongest is, of course, Ardor, followed by Cristina, Shu Ru, Bora, Rosea, and Ho Qing.
Cristina, especially, had a unique spear technique which greatly empowered her and allowed her realm to jump by a few grades. Furthermore, her black spear was a 2nd grade Mysterious-ranked artifact, something which is very rare to find, even in the richest sects.
Before he brought them to this training ground, Arthur had a small talk with each and every one of them and, apparently, the two friends, Cristina and Bora, deserted their sects due to some 'complications' and vowed to never betray Arthur if he protects them, which he agreed, obviously.