From WoWWiki

Siphon Life
Siphon Life Instant cast 30 yds range 410 Mana at max level Transfers X health from the target to the caster every 3 sec. Lasts 30 sec.
Usable By
Class	Warlock
Properties
Type	Offensive, Defensive
School	Shadow
Cooldown	None/Global Cooldown
Talents
Talented	Yes
Talent Tree	Affliction, Tier 5
Talent Required	Siphon Life
Improvement Talents	Demonic Sacrifice (Succubus), Grim Reach, Master Demonologist (Succubus), Shadow Mastery, Soul Link, Suppression
Other Information
Ranks	6
Related Buff
Magic Siphon Life Drains X health to the caster every 3 secs. Duration: 30 sec

Gouts of blood erupt from a victim's eyes, nose and mouth. The streams spin and twist into a single, larger, rope-like stream as they bridge the gap between the target and the caster. The caster opens his mouth and draws in the stream, gaining vitality as the victim weakens.^{M&M 98}

Siphon Life is a Shadow-based Damage over Time warlock spell that heals for the damage done. It is only obtainable from the Affliction talent tree via the same-named talent.

Rank	Mana Cost	Health per tick	Level	Cost
1	140	15	30	Talent
2	190	22	38	4 50
3	250	33	48	6 30
4	310	45	58	10 80
5	350	52	63	22 50
6	410	63	70	22 50

Notes

• There are ten 3-second ticks, beginning 3 sec after casting Siphon Life.
• Siphon Life already causes sensible threat upon application.
• In Patch 2.3, the amount healed is reduced when the warlock is affected by healing reducing effects (e.g. Mortal Strike, Wounding Poison).

See Life Drain for more details.

Talent improvement

Demonic Sacrifice (Succubus), Master Demonologist (Succubus), Shadow Mastery, and Soul Link increase damage.

Grim Reach increases range and Suppression reduces chance to resist.

With Shadow Embrace, this spell also reduces physical damage dealt by the target.

Tips and tactics

Siphon Life and Life Tap can be used to easily regenerate mana and health. It just needs to be spammed on multiple targets, while regularly life tapping the newly gained life into mana.

Siphon Life and Drain Life can be used to quickly regenerate health or to "Drain-Tank" an enemy.

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