From wow.incgamers.com

Statistics

Talent Improvements

The talents below affect Demon Skin in the following ways:

Affliction Tree

Talent: Improved Drain Soul
Effect: Returns mana if target is killed by you while you drain its soul. Also, Affliction spells generate less threat.
Statistics: 1 point = returns 7% mana & 5% less threat. 2 points = returns 15% mana with 10% less threat.

Threat Level

Insert threat level of Demon Skin.

Facts about Demon Skin

• Warlocks begin the game with level one of this skill.
• Replaced by Demon Armor which the Warlock can learn at level 20.