When all the smaller monsters were defeated, Seven Star Warrior had reached Level 39. As for the rest, they received a good amount of experience points but not enough to gain a level. Jiang Fei predicted that after the final circle in the hall was defeated, he might gain a level.
As for the Dark Tortoise in front of him, Jiang Fei started to grind his brain to think of a plan to fight. On the plus side, the boss had low attack but the skill effect was powerful enough to kill Cloth Armor player.
This battle placed priority on attack sequence. Once the boss hides into its shell, everyone must stop attacking or else they would trigger the boss' skill.
To be fair, all other boss before this one was harder. The most important thing to take care of was everyone's health point. No one can have less than 5,000 health points or they would be killed and in turn restore the boss health.