The Palace Gambit.

Two sisters enter the palace and quickly earn the emperor’s favor, but their rise ends in tragedy when the elder sister—pregnant with the heir—is killed in a palace scheme. Left with nothing, the younger sister Lu Jiuning hides her grief and, as a lowly palace maid, carefully plots her revenge. Moving between rival consorts and imperial power, she wages a quiet but ruthless battle to avenge her sister’s death.