Monster Heal is a monster attribute that does as it implies; it allows them to heal life back over time after being injured.
The speed at which a monster regenerates its life depends on various things. Most crucially is the difficulty of the game you are playing in. Another factor is their HP total; the regeneration is a percent of their maximum life - in other words, the more life a monster possesses, the more it heals each second.
Diablo/Hellfire[]
Monster Heal is something not many players may know about in Diablo I. The only ways to really notice that such a thing exists is through one of Pepin's randomized gossip lines, or extensive use of Golem. And even then, it is generally not too big of a hindrance (or an aid, in Golem's case), because within the time such regeneration would be useful, the monster is simply overwhelmed by the player's damage.
Unfortunately, for those few who do not have enough of an edge, Prevents Monster Heal is not available in the first game, even with Hellfire installed. Equip your hero with that in mind.
Diablo II/Lord of Destruction[]
In Diablo II and Lord of Destruction, Monster Heal is much more of a boon to the minions of Hell (or to you, if it's your Hireling or Summons), because while they did not regenerate while the hero was in town in the original Diablo, they will in Diablo II as well as the expansion. Another factor to that regeneration is the actual monster type; that is to say, a Minion of Destruction in Nightmare Difficulty may regenerate faster than a Steel Scarab in Hell Difficulty.
There are a couple ways to counter monster regeneration, however. Unlike the original Diablo, "Prevents Monster Heal" does exist, in an easily obtainable affix for both Magic and Rare Melee Weapons. Alternatively, the regeneration can be counteracted with the damage over time effects of poison or the even better Open Wounds that does bleeding damage over 8 seconds and scales with your hero's level, usually inflicting more than enough to prevent the monsters' regeneration.
List[]
The following is a list of all items with "Prevent Monster Heal":
- Malice — Rune Word (rlvl 15)
- Edge — Rune Word (rlvl 25)
- Blacktongue — unique Bastard Sword (rlvl 26)
- Woestave — unique Halberd (rlvl 28)
- The Grim Reaper — unique War Scythe (rlvl 29)
- The Impaler — unique War Spear (rlvl 31)
- Spineripper — unique Poignard (rlvl 32)
- Hwanin's Blessing — set Belt (rlvl 35)
- Fleshrender — unique Barbed Club (rlvl 38)
- Headstriker — unique Battle Sword (rlvl 39)
- Unbending Will — Rune Word (rlvl 41)
- Blackhorn's Face — unique Death Mask (rlvl 41)
- Husoldal Evo — unique Bec-De-Corbin (rlvl 44)
- Oath — Rune Word (rlvl 49)
- Venom — Rune Word (rlvl 49)
- Mosaic — Rune Word (rlvl 53)
- Kingslayer — Rune Word (rlvl 53)
- Call to Arms — Rune Word (rlvl 57)
- Grief — Rune Word (rlvl 59)
- Beast — Rune Word (rlvl 63)
- Wrath — Rune Word (rlvl 63)
- Infinity — Rune Word (rlvl 63)
- Bonehew — unique Ogre Axe (rlvl 64)
- Fury — Rune Word (rlvl 65)
- Brand — Rune Word (rlvl 65)
- Famine — Rune Word (rlvl 65)
- Last Wish — Rune Word (rlvl 65)
- Destruction — Rune Word (rlvl 65)
- Doom — Rune Word (rlvl 67)
- Lacerator — unique Winged Axe (rlvl 68)
- Fleshripper — unique Fanged Knife (rlvl 68)
- Nature's Peace — unique Ring (rlvl 69)
- Breath of the Dying — Rune Word (rlvl 69)
Diablo III[]
Although Monster Heal is no longer around in Diablo III, before a patch, if the Nephalem fell in battle against a Rare, Champion or Unique, that monster group could heal itself to full. This frustrated too many players however, resulting in Monster Heal being removed.
The only other way a monster can heal is the Vampiric affix, and even that affix can only happen on legacy Elites.
Bosses will heal to full if they defeat players though, forcing them to begin the fight from scratch.
Innate monster abilities may allow them to renew in battle: Morlu (of either type) may partially heal if they are brought near death (into their ash state), but not killed quickly afterwards.