Final answer:
The king had the princess' lover put into the arena of the king.
Step-by-step explanation:
When accused of a crime, the accused would be put into an arena with two doors. Behind one door was a tiger, and behind the other door was a lady. In the context of this question, when the king discovered the princess was involved in a love affair, the king had the princess' lover put into the arena of the king.
Learn more about Crime and punishment in historical settings