That's right, the name of the empire is the Life Empire, whether this counts as a kind of dark humor is unknown.
In any case, when many people hear this name, their expressions become very strange. An empire established by the Undead would logically be called the Death Empire, but calling it the Life Empire is indeed odd.
The official explanation given is that within our empire, all life is completely equal.
Of course, whether it is truly equal is unknown to them, but various ranks within the empire are based on strength and contributions, not race. Regardless of whether a race is on the surface or underground, it is treated the same, even the Undead.
Of course, it is understandable that some races are naturally strong, while others are naturally weaker.
