Complete level one.
Complete level two.
Complete level three.
Complete level four.
Complete level five.
Complete level six.
Complete level seven.
Complete level eight.
Disintegrate 50 skeletons. (One session, kills carry over on death.)
Disintegrate 100 skeletons. (One session, kills carry over on death.)
Disintegrate 25 skeletons. (One session, kills carry over on death.)
Disintegrate ten skeletons. (One session, kills carry over on death.)
Disintegrate one skeletons. (One session, kills carry over on death.)
Disintegrate ten skeletons in under four minutes.