In 1 Chronicles 15:29And it came to pass, as the ark of the covenant of the LORD came to the city of David, that Michal, the daughter of Saul looking out at a window saw king David dancing and playing: and she despised him in her heart.
See All...-- It states that "Michal" is Saul's daughter and that she saw King David out of a window and she despised him. Who was she and what happened to her after Saul and his family were killed?

In hope that David would be killed in the act, Saul offered his daughter Michal to David for the dowry of 100 killed Philistines. David doubled the request by killing 200 Philistines and Saul had to follow through with his offer (1 Samuel 18:20-28 [20] And Michal Saul's daughter loved David: and they told Saul, and the thing pleased him. [21] And Saul said, I will give him her, that she may be a snare to him, and that the hand of the Philistines may be against him. Wherefore Saul said to David, Thou shalt this day be my son in law in the one of the twain. [22] And Saul commanded his servants, saying, Commune with David secretly, and say, Behold, the king hath delight in thee, and all his servants love thee: now therefore be the king's son in law. [23] And Saul's servants spake those words in the ears of David. And David said, Seemeth it to you a light thing to be a king's son in law, seeing that I am a poor man, and lightly esteemed? [24] And the servants of Saul told him, saying, On this manner spake David. [25] And Saul said, Thus shall ye say to David, The king desireth not any dowry, but an hundred foreskins of the Philistines, to be avenged of the king's enemies. But Saul thought to make David fall by the hand of the Philistines. [26] And when his servants told David these words, it pleased David well to be the king's son in law: and the days were not expired. [27] Wherefore David arose and went, he and his men, and slew of the Philistines two hundred men; and David brought their foreskins, and they gave them in full tale to the king, that he might be the king's son in law. And Saul gave him Michal his daughter to wife. [28] And Saul saw and knew that the LORD was with David, and that Michal Saul's daughter loved him.
See All...). After they were married, Michal protected David when Saul sought to kill him and helped him escape her father's wrath (1 Samuel 19:10-18 [10] And Saul sought to smite David even to the wall with the javelin: but he slipped away out of Saul's presence, and he smote the javelin into the wall: and David fled, and escaped that night. [11] Saul also sent messengers unto David's house, to watch him, and to slay him in the morning: and Michal David's wife told him, saying, If thou save not thy life to night, to morrow thou shalt be slain. [12] So Michal let David down through a window: and he went, and fled, and escaped. [13] And Michal took an image, and laid it in the bed, and put a pillow of goats' hair for his bolster, and covered it with a cloth. [14] And when Saul sent messengers to take David, she said, He is sick. [15] And Saul sent the messengers again to see David, saying, Bring him up to me in the bed, that I may slay him. [16] And when the messengers were come in, behold, there was an image in the bed, with a pillow of goats' hair for his bolster. [17] And Saul said unto Michal, Why hast thou deceived me so, and sent away mine enemy, that he is escaped? And Michal answered Saul, He said unto me, Let me go; why should I kill thee? [18] So David fled, and escaped, and came to Samuel to Ramah, and told him all that Saul had done to him. And he and Samuel went and dwelt in Naioth.
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However, while David was in exile because of this personal danger, Saul gave Michal to another man as a wife; to Phalti the son of Laish (1 Samuel 25:44But Saul had given Michal his daughter, David's wife, to Phalti the son of Laish, which was of Gallim.
See All...). We are not told how readily Michal went along with this marriage. In later years, when David was king of Judah but not the northern tribes, Abner, the captain of the host of the northern tribes offered to bring these tribes to David. As a prerequisite for any agreement, David demanded the return of Michal as his wife. She was taken from her second husband and given back to David (2 Samuel 3:12-16 [12] And Abner sent messengers to David on his behalf, saying, Whose is the land? saying also, Make thy league with me, and, behold, my hand shall be with thee, to bring about all Israel unto thee. [13] And he said, Well; I will make a league with thee: but one thing I require of thee, that is, Thou shalt not see my face, except thou first bring Michal Saul's daughter, when thou comest to see my face. [14] And David sent messengers to Ishbosheth Saul's son, saying, Deliver me my wife Michal, which I espoused to me for an hundred foreskins of the Philistines. [15] And Ishbosheth sent, and took her from her husband, even from Phaltiel the son of Laish. [16] And her husband went with her along weeping behind her to Bahurim. Then said Abner unto him, Go, return. And he returned.
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When David brought the ark of the covenant to Jerusalem and rejoiced in the streets with the people, Michal strongly criticized him for his crudeness and lowness (2 Samuel 6:20-23 [20] Then David returned to bless his household. And Michal the daughter of Saul came out to meet David, and said, How glorious was the king of Israel to day, who uncovered himself to day in the eyes of the handmaids of his servants, as one of the vain fellows shamelessly uncovereth himself! [21] And David said unto Michal, It was before the LORD, which chose me before thy father, and before all his house, to appoint me ruler over the people of the LORD, over Israel: therefore will I play before the LORD. [22] And I will yet be more vile than thus, and will be base in mine own sight: and of the maidservants which thou hast spoken of, of them shall I be had in honour. [23] Therefore Michal the daughter of Saul had no child unto the day of her death.
See All...). As a judgment, Michal had no child from that day unto the day of her death. Most Bible scholars think that this also means that David no longer had physical relations with her. The judgment may seem harsh but it is unlikely that this was a one-time offhanded remark. It was simply a window into her heart and revealed the bitterness that had permeated there.

The only mention of Michal after this time is in 2 Samuel 21:8But the king took the two sons of Rizpah the daughter of Aiah, whom she bare unto Saul, Armoni and Mephibosheth; and the five sons of Michal the daughter of Saul, whom she brought up for Adriel the son of Barzillai the Meholathite:
See All... - "But the king took the two sons of Rizpah the daughter of Aiah, whom she bare unto Saul, Armoni and Mephibosheth; and the five sons of Michal the daughter of Saul, whom she brought up for Adriel the son of Barzillai the Meholathite." Famine had come on the land of Israel because of Saul's mistreatment of the Gibeonites. When David asked what they required for restitution, the Gibeonites demanded the death of seven of the descendants of Saul. Five of those offered were the sons of Michal's sister, Merab, and Adriel. It is probably that both Adriel and Merab had died and that Michal took on the care of her five nephews. This was another terrible blow to a decidedly sad life. There was evidently no love lost between David and Michal. Although he protected Mephibosheth, he readily offered the five nephews that Michal had brought up.

We hear nothing else of Michal in the Bible. We can only assume that she died as she lived, a bitter and unhappy soul. Those who do not learn to rejoice in the Lord will be destroyed by the root of bitterness.