C2027 Upgrade Servant from Strength to Strength

Looking at the energy tower that was gradually filling up, Chu Tian felt a heartache in his heart.

Why didn't he find any undead mines that could be used to fill up the energy tower? He had thought that this thing was trash, so he had used it to upgrade other special buildings. But now, Chu Tian felt that he had lost a lot of it.

However