Core rule
Resistance, Vulnerability, and Immunity
Resistance halves damage of the relevant type, Vulnerability doubles it, and Immunity prevents that damage.
Check the type involved. Fire resistance does not also reduce Cold or Piercing damage.
Multiple resistances to the same damage do not repeatedly halve it. Other damage reduction and effects that ignore resistance have their own conditions.
Resistance5Normal10Vulnerability20Immunity0
No other damage reduction or modifiers are included.