The Crimson BladeEP 18

Ye Qingling, an illegitimate daughter of the Ye family, is forced to marry the critically ill heir of a noble house. On their wedding night, the heir suddenly dies, and she narrowly escapes being sacrificed as a burial companion for the Grand Princess. To survive, she risks approaching her cold-hearted brother-in-law, Wei Hengzhi, through a fake pregnancy scheme and careful schemes. Yet, she becomes entangled in a forbidden attraction between sister-in-law and brother-in-law, and a whirlpool of political intrigue. In the end, Wei Hengzhi's true identity as a hidden royal prince is revealed. Together, they crush the conspiracy. He ascends the throne as emperor, and she becomes his empress.