Level 13:
(D) Dark Bargain:
(New effect) Life Tap consumes 15% less Health and grants 15 Armor for 6 seconds. Drain Life extends the duration by 1 second for each second it is active.
Level 20:
(R) Cipher of Damnation (Replaces Deep Impact):
Every 2 seconds a meteor will fall on the current location of enemy Heroes within the area. Ability can be channeled to cause Rain of Destruction to last indefinitely. Does not extend it's current duration.
(Passive) The Master's Power (New):
Cooldown of Heroic Abilities is reduced by 25% and Gul'dan's maximum Health is increased by 10% but his Death timer is increased by 15 seconds.
Heroes of the Storm Build Guides
Life Tap consumes 15% less Health and grants 15 Armor for 6 seconds. Drain Life extends the duration by 1 second for each second it is active.
Summon a rain of meteors in an area over 6 seconds. Each meteor deals 145 (+4% per level) damage in a small area. Staying in the area allows Gul'Dan to extend the duration by up to 3 seconds.
Every time a hero is damaged by Rain of Destruction, their Armor is reduced by 3 for 6 seconds, up to a maximum of 15. Lower the cooldown of Rain of Destruction by 0.5 seconds for every enemy Hero hit.
Just some wording changes, and also i think Rain of Destruction reducing Armor at 20 would be far better, as it can compete with Haunt