The key lies in the description of this Skill Book, "Survive for seven days, after which it will naturally dissipate." The word 'survive' is used here, which seems somewhat ironic for an Undead. Is the description of the skill not accurate enough? Xiao Buli didn't think so.
Playing this game for so long, he had almost completely grasped the operation of the game. There were basically no bugs.
Then it is very likely that the so-called Wandering Spirit is not just a common Undead, but a kind of creature. As such a creature, could a Wandering Spirit be resurrected? He had always subconsciously thought it was possible, but now he found it hard to confirm. After all, if Spirit Reincarnation was really that useful, there's no way the Skill Book would be so cheap.
One has to know, the probability of a person becoming a Ghost after death is not one hundred percent, having such a skill would be like having an extra insurance policy.