Idol of C'Thun

In the Shadow Priest talent tree, Idol of C'Thun sits in the Shadow specialization talents, row 10 of 11. It is a single-point node. Its row opens once 20 points are spent in Shadow Talents.

Connected above

The tree draws a line into Idol of C'Thun from Insidious Ire and Crushing Void.

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  Insidious Ire2 ranks

  While you have Shadow Word: Pain, Shadow Word: Madness, and Vampiric Touch active on the same target, your Mind Blast, Void Torrent, Mind Flay, and Void Volley deal 20% more damage.

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  Crushing Void

  Tentacle Slam deals 50% increased damage and Void Volley deals 15% increased damage. When Voidform ends, you can cast Void Volley 1 additional times within 30 sec.

Same row

Also on this row: Idol of Y'Shaarj, Idol of N'Zoth and Idol of Yogg-Saron.

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  Idol of Y'Shaarj

  While Shadowfiend, Mindbender, or Voidwraith are active, your haste is increased by 10%.

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  Idol of N'Zoth

  You create Horrific Visions when casting harmful spells on enemies. At 50 stacks of Horrific Visions, your target sees a nightmare, dealing (182% of Spell Power) Shadow damage and granting you 2.03333 Insanity over 3 sec. At 100 stacks, your target witnesses a vision of N'Zoth, dealing (689% of Spell Power) Shadow damage and granting you 6.1 Insanity over 3 sec.

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  Idol of Yogg-Saron

  After conjuring Shadowy Apparitions, gain a stack of Idol of Yogg-Saron. At 20 stacks, you summon a Thing from Beyond that casts Void Spike at nearby enemies for 20 sec. Hurls a bolt of dark magic, dealing (93.9% of Spell Power) Shadow damage and Shadow damage to all enemies of the target. Damage reduced beyond 5 targets.