Wikia

Health Funnel
Health Funnel (Racial) 45 yd range Channeled Sacrifices 2% of your maximum health to restore 6% of your summoned Demon's maximum health every 1 sec. Lasts for 6 sec.
Usable by
Class	Warlock
Race	Channeled
Properties
Type	Utility
School	Shadow
Cooldown	(GCD 1.5 sec)
Level required	11
Related buff
Health Funnel Transferring Life. Duration: 6 seconds

Health Funnel is a core warlock ability learned at level 11. It allows warlocks to transfer their own health to their pet.

Modified by

2020

Glyph of Health Funnel
Item Level 25Disenchants into:
Not disenchantable
Minor Glyph
Classes: Warlock
Requires Level 25
Use: Permanently teaches you this glyph.
Your Health Funnel instantly restores 15% of your demon's health, but has a 10 sec. cooldown.
Sell Price: 1

Useful, and unlike First Aid, this can be used during combat, which generates aggro for the Warlock (although this may be desirable if the pet is dying anyway).
It is possible for warlocks to kill themselves using this spell.

Patch 2.4.3 (2008-07-15): This ability will now cancel channeling when the target pet is Banished.
Patch 2.3.2 (2008-01-08): The health cost taken from the Warlock after using Health Funnel will now remain consistent between uses.
Patch 2.0.3 (09-Jan-2007): Now scales with equipment.