Mind Sear and Shadow Word: Pain damage has a 4% chance to grant you Coalescing Shadows and Mind Flay has a 15% chance to grant you Coalescing Shadows, stacking up to 3 times.
Mind Blast and Mind Spike consume all Coalescing Shadows to deal 10% increased damage per stack, and consuming at least 1 increases the damage of your periodic effects by 10% for 15 sec.