Priest · Shadow Magic · tier 6 · from level 35
Early Demise
+66.0 Shadow Word: Death
2/2 · level 60 · per cast · on targets at or below 20% health
Early Demise
Rank 2/2
Increases Shadow Word: Death's critical strike chance on targets at or below 20% health by 30%.
Averages, counting crits and misses, for a level 60 Priest with a typical weapon and no other gear or buffs, against a target your level. Worked out from the game's own data, the same way as the Foresight addon.