Whenever you hit with Death Strike or Obliterate, there is a X% chance that the Frost and Unholy Runes will become Death Runes when they activate.
Death Rune Mastery is a Death knight talent located in the 3rd tier of the Blood Tree. It causes Death Strike and Obliterate to convert the frost and unholy runes to death runes, which count as any type of rune. With proper use of Blood Tap, this talent can set you up to unleash as many as eight consecutive Heart Strikes.
Because this is near the top of the blood tree, frost and unholy specs may reach this talent and create a spec that could generate six death runes, however, there is very little information about the rotation and stats required for any such spec.
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