As described in Ⅰ M'lachim 22 and Ⅱ Divre Hayamim 18, King Ach'av of Yisrael (the northern kingdom) suggested that King Y'hoshafat of Y'huda join him in battle against Aram. A number of Baal-prophets prophesied that they would be successful and should go to battle, but Y'hoshafat wanted to know what a Hashem-prophet had to say. So they fetched Michayhu ben Yimla. He prophesied that they would be unsuccessful in the battle against Aram (if they went) and should not go. Ach'av heard that but was certain of victory, so he ordered Michayhu jailed until such time as he (Ach'av) would return from battle victorious.
Ach'av died in battle.
What then happened to Michayhu: was he released from prison? killed? allowed to rot there? And why? And, if he was released or killed, under what circumstances and when?