Micaiah, the son of Imlah, was a prophet of God who served King Ahab, despite Ahab not liking him due to him never prophesying anything good about the king. He will only speak what the LORD will have him to speak.
When Ahab entreated King Jehoshaphat to join him in a military campaign to retake Ramoth Gilead from the Syrians, Jehoshaphat accepted and offered his military strength to Ahab's, but said that they should inquire of the LORD first. Ahab brought all his prophets together and asked them if they should attack Ramoth Gilead or refrain, and they all told him to attack, assuring that the LORD will deliver it to him. Jehoshaphat wasn't convinced and asked if there was a prophet of the LORD they can inquire by. Ahab told him about Micaiah, who never prophesies anything good about the king. Nonetheless, he sent his servants to get Micaiah while he and Jehoshaphat sat on their thrones and watched the prophets prophesy, with Zedekiah son of Chenaanah using iron horns to illustrate how the king will destroy the Syrians.
When Micaiah came, King Ahab asked him if he and Jehoshaphat should attack Ramoth Gilead or refrain, and Micaiah answered, "Go and prosper, for the LORD will deliver it into the hand of the king!" Ahab detected the sarcasm in the answer and told Micaiah to answer him with nothing but truth, and so Micaiah told the king that he saw all of Israel like sheep scattered on the mountains with no shepherd, and the LORD said to let them return to their house in peace. He also revealed that God had sent a lying spirit into the mouths of Ahab's prophets in order to bring disaster upon the king. At this, Zedekiah slapped Micaiah's face and asked where the Spirit of the LORD went from himself to speak to him, and Micaiah told Zedekiah he will know when he goes into an inner room to hide himself. Not pleased with the answer, King Ahab ordered his servants to put Micaiah in prison and feed him nothing but bread and water until he returns in peace. Micaiah warned Ahab that if he did return in peace, then the LORD hasn't spoken through Micaiah.
Though Ahab tried to escape the prophesied fate by disguising himself as a soldier while Hezekiah wore his royal robes in the battlefield, a random arrow shot pierced through his armor and killed him.