Turn 1: play Boulevard of Bones then make a skeleton with the Necromancer.

Turn 2: play Open Grave or Open Mausoleum, make a skeleton with it, make another skeleton from Boulevard of Bones then make another skeleton with the Necromancer.

Turn 3: play Open Grave or Open Mausoleum, make a skeleton with it, make another skeleton from Boulevard of Bones then make another skeleton with the Necromancer.

Turn 4: play Open Grave or Open Mausoleum, make a skeleton with it, make another skeleton from Boulevard of Bones then make another skeleton with the Necromancer.

Turn 5: you now have ten skeletons and are ready to make more skeletons.