Instructions
Ensure Shadowform is active. Shadowform increases all shadow damage you deal by 15 percent, reduces all damage you take by 10 percent and increases the speed with which your spells are cast by five percent; however, because you can't cast holy spells while in Shadowform, it automatically becomes inactive if you heal yourself or others, or resurrect somebody.
Cast Shadow Word: Pain and Devouring Plague on your target, then cast Mind Blast, and Mind Flay.
Continue casting Mind Flay until Mind Blast is available again, then cast Mind Blast.
Continue casting Mind Flay and Mind Blast, refreshing Shadow Word: Pain and Devouring Plague when they expire, until your target's health is low enough that a single Shadow Word: Death will kill it.
Cast Shadow Word: Death.