The unique passive is considered health regeneration and is therefore not affected by effects that do not interact with health regeneration (i.e Revitalize). Effects that do modify health regeneration also modify the passive - for example Sion'sGlory in Death which multiplies his health regeneration by 0 for the duration of the effect, thus effectively disabling the passive.
The living armor protected the greatest troll warrior in the entire realm during the bloodiest and most devastating battles of the Rune Wars. Deep within the dark woods of Crystone the living armor waits to protect its next owner. A word of warning required before seeking out Warmog... it will protect you for a time, but when it grows tired of you, who will protect you from it?
The previous unique passive used to belong to the removed item Force of Nature.
Self-inflicted damage and the Nexus Obelisk will not disable the Unique passive.
At roughly 40,000 maximum health, the health regeneration from this item's passive alone is enough to withstand the Nexus Obelisk indefinitely, since it will stay active despite the constant damage, and heal it back at the same rate.
Stats: 800 health, 200% base health regeneration, 10 ability haste.
Unqiue Passive - Warmog's Heart: If you have at least 3000 maximum health, regenerates 5% maximum health every second if you haven't taken damage from champions in 6 seconds (3 seconds for damage from non-champions).
Passive changed to: Permanently gain 4.5 health and 0.15 health regeneration per 5 seconds per minion kill. Champion kills and assists grant 45 health and 1.5 health regeneration per 5 seconds. Bonuses cap at +450 health, and +15 health Regen per 5.