Elements and Monsters
Monsters may have an Immunity, Resistance, or Vulnerability to a damage type, like an element (Dark, Earth, Fire, Ice, Light, Shock, or Water), or a type of physical damage (Blunt, Sharp, or Piercing).
A Vulnerability means the creature takes an extra 4 damage when struck by that element, and can’t reduce the total damage below 4.
Resistances to a damage type come in Ranks; every Rank of Resistance reduces the damage from attacks of that type by 2 (before Defense and Reactions; minimum 1).
Generally, Monsters should not have both a Resistance and a Vulnerability to the same type of damage (except for the rare case where a Monster is aware of their weakness, and has taken steps to shore it up).
For more on Resistance, see Status Effects.
For more on Vulnerability, see Vulnerability.
A note for Swarms: Each Rank of Resistance reduces the number of squares destroyed by 1 (minimum 1). Attacks the Swarm has a Vulnerability to destroy an additional square of the Swarm. If the Swarm has both, divide the Rank of Resistance by 2.
Immunity to a type of damage means that all attacks of that type deal 0 damage to the creature, regardless of other damage types, Vulnerabilities, or other effects. No creature should be Immune to more than a single type of damage!
As a guideline, most Monsters should only have up to three kinds of Vulnerabilities or Resistances, in total.