I've looked around and can't find an answer to this.
Tomb Kings are a neutral force, neither Order nor destruction. The rule book phrases it to suggest that you can choose to be either.

Taking that as a given if I choose to play a Tomb Kings army as an Order army what happens if I use a Liche priest with the Lore of Light to cast the presence spell "Enlightenment"? As it stand my undead units will become unbreakable correct?

Do we think this was just an oversight and the uselessness of this spell in these circumstances was not noticed or have I missed something obvious?

Thanks for the assist.