Maddening Touch
Vampiric Touch deals 20% additional damage and has a chance to generate 1 Insanity each time it deals damage.
Tree position
In the Shadow Priest talent tree, Maddening Touch sits in the Shadow specialization talents, row 6 of 11. It is a single-point node. Its row opens once 8 points are spent in Shadow Talents.
Connected above
The tree draws a line into Maddening Touch from Voidform, Shadowy Insight and Voidtouched.
VoidformBombards your target with a Void Volley and twists your Shadowform with void magic, increasing your spell damage by 20% for 20 sec. During Voidform, Void Volley replaces this spell and can be used up to 3 times. Releases a volley of pure void energy, firing 10 bolts at your target and 1 boltsbolt at all enemies of your target for (95.4% of Spell Power) Shadow damage. Generates 10 Insanity.
Shadowy InsightShadow Word: Pain periodic damage has a chance to cause your next Mind Blast to be instant and ignore its cooldown.
VoidtouchedIncreases your Shadow Word: Madness damage by 6% and increases your maximum Insanity by 50.
Connected below
Maddening Touch leads on to Mastermind and Mind's Eye or Distorted Reality.
Mastermind2 ranksIncreases the critical strike chance of Mind Blast, Mind Flay, and Shadow Word: Death by 4% and increases their critical strike damage by 20%.
Mind's EyeReduces the Insanity cost of Shadow Word: Madness by 5.
Distorted RealityIncreases the damage of Shadow Word: Madness by 20% and causes it to deal its damage over 12 sec, but increases its Insanity cost by 5.
Same row
Also on this row: Shadowfiend, Dark Thoughts, Improved Voidform or Ancient Madness, Shadeburst, Dark Evangelism and Shattered Psyche.
ShadowfiendShadow Word: Death has a 40% chance to summon a Shadowfiend for 5 sec when damaging targets below 20% health. Summons a Shadowfiend to attack your target for 5 sec. Generates 1 Insanity each time the Shadowfiend attacks.
Dark ThoughtsIncreases the chance for Shadowy Insight to occur by 25%. When consuming Shadowy Insight, Mind Blast generates 1 additional Insanity.
Improved VoidformVoidform increases your spell damage by an additonal 5% and grants 2 additional uses of Void Volley.
Ancient MadnessWhen Voidform ends, the haste lingers and decays over 10 sec.

Dark EvangelismIncreases your periodic spell damage by 6%.
Shattered PsycheLasts 10 sec.
Talent trees
Maddening Touch is in the talent tree of 3 specializations. Priest: Discipline (Healer), Holy (Healer), Shadow (DPS).
Maddening Touch Changes by patch
Tracked changes to this talent between game data builds, newest first.
- First tracked in the game data (patch 12.1.0)