Immune

Immunities, and skills or items that could "break" them were a major part of the character strategy in Diablo II. Immunities will not be present in Diablo III.

Monsters in Diablo III may have very high resistances, but the team doesn't want to make killing them literally impossible for some character builds. Just very, very difficult. It will still be a good idea for players to build their characters with a variety of damage types, to use as the situation requires. This will be easier in Diablo III than in Diablo II, thanks to the skill diversifying nature of runestones.

Diablo III Immunities

Jay Wilson confirmed during a Developer Chat in 2012 that Monsters won't have immunities as an affix.[1]

Jay Wilson: We do not use immunities as a monster affix. We focused more on powers that change up the monster’s threat and challenge different classes in different ways.

Jay Wilson answered a question about resistance and immunities during the BlizzCon 2010 Panel: Open Q&A:

Jay Wilson: Resistance was changed from a flat percentage to a basically a rating, that works how defense did (in Diablo II). It scales with the level of the monster. So it can grow to higher values over time. With this change we do not have to include resistance penalties for Nightmare and Hell, as was done in Diablo II. In a lot of ways our resistances are the same. Resistance is still a big part of the game. It's a focus of your defensive building of your char in higher levels.

As for immunities, we're not doing double/triple immunities (in monsters). We don't want to completely hurt a character's ability to hurt something. We also diversify damage types more across the classes (than was done in Diablo II). But we still can't count on a class having a diversity of damage types we can use.

Question: Will characters need to stack resistances for particular fights?

Jay Wilson: Sometimes. It's kind of an end game question, so haven't done it yet. We'll look more at it as the time comes closer.

Character Skills

Only a few characters skills are known to lower resistances or break immunities, and these are very subject to change as game development continues.

Wrath of the Berserker -- Barbarian This shout grants higher stats and enables the Barbarian to partially break monster immunities.

• Description: Enter a heightened sense of fury, raising several stats (Critical Hit, Attack Speed, Dodge Chance, Movement Speed) for X seconds. Monsters with damage immunities will take X% less damage from the Barbarian's attacks rather than being immune.