Immunity is a status modifier that renders a character completely resistant to a specific damage type (although it is usually associated with the Poison attribute).
Game Specific InformationEdit
Castlevania: Symphony of the NightEdit
Symphony of the Night is the only Castlevania game to differentiate between immunities and resistances, as enemies are capable of having both. However, a monster with an immunity to a certain damage type will not take damage from attacks having that attribute (for example, if the player attacks a Slime with a weapon that has the Cut attribute, it will not take any damage).
Immunity against Stone works a bit different from other elements. Immunity against Stone (due to the Medusa Shield or Mirror Cuirass) only reduces Stone damage taken by Alucard to 1. This case does not happen to enemies such as Richter Belmont and blue Medusa Heads.
In the most recent Castlevania games, immunities have become associated with player characters rather than enemies, and are almost always related to status-modifying damage types. There is not a clear distinction between immunities and resistances, but a player with a high resistance to a damage type is said to be immune to it.