Blightfall

In the Unholy Death Knight talent tree, Blightfall sits in the Unholy specialization talents, row 10 of 11. It is a single-point node. Its row opens once 20 points are spent in Unholy Talents.

Connected above

The tree draws a line into Blightfall from Scourging.

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  Scourging2 ranks

  Scourge Strike now causes your Plagues to erupt at 65% effectiveness. Clawing Shadows can now stack 1 additional times.

Same row

Also on this row: Lord of the Dead and Outnumber.

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  Lord of the Dead

  Putrefying a Lesser Ghoul has a 100% chance to reanimate it as a Magus of the Dead who hurls Frostbolts and Shadow Bolts at your foes for 15 sec. When you control 3 Magus of the Dead, sacrifice them to summon their Lord of the Dead for 15 sec, casting Frostbolts that chain between enemies. Magus with higher remaining duration grant increased power.

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  Outnumber

  Each Lesser Ghoul increases the damage of your permanent Ghoul by 10%, and Dark Transformation additionally empowers the Claw attacks of your Lesser Ghouls to Sweeping Claws. Rakes an enemy with deformed claws, dealing Shadow damage to the target and Shadow damage to nearby enemies.