You can use flashback, thoughts, or even discussion with other character while the lich tell the truth but everyone thought he lying, or you can even go with the misunderstanding type of discussion where everything the lich said is understand differently.
I don't think there any rules against that, it's fictions write what you want. Unless you glorify these acts, but even if you do it, if it's in the antagonist side or have a mean in the story I don't think there will be any problems with the rules.
My story are build with innate ability, but the cultivation inside it make those said ability evolve through the ranks in the way each individual "want" somehow.
There tons of stories who use the innate ability system and are good, the characters inside these stories try to master these...