Buried Relic is a dungeon in Mystery Dungeon: Red Rescue Team And Blue Rescue Team that has 99BF. It also is the home of Regirock, Regice and Registeel. They can be recruited after clearing the dungeon at least one time. Mew can be found here and can be recruited. You also need the Music box that you retrieve from the rock ice and steel parts that you get from the Regis.