These were some of the powerful wizarding families. They were destroyed as they did not agree to join the Dark Lord in his activities. Whoever resisted to join the Dark Lord would be killed. These families set as a good example for all of us. They stood up to him and fought bravely.
Merlin lived a long time ago in Britain where Kings and Queens still existed. He was even before the time of King Arthur and The Knights of The Round Table. Merlin was a very formidable wizard too. It was rumoured that he was sent to receive King Arthur and to convince the Knights of Britain that Arthur of Camelot was their King. The short wizard, usually prefers to wear purple robes and pointed hat, was the one who delivered the whole of Great Britain from civil wars and gave his advice to Kings before and after King Arthur. Recent discoveries show that Merlin has not yet died but is living in the Land of Everlasting, together with the elven ones.