Actually the cards apply to different attributes. Unavoidable only refers to the Defense attribute.
Defenses
The gold shield icon represents a Defense attribute. The large number at the top of the shield shows how
effective the Defense is. You cannot use a Defense against an attack that has the Unavoidable trait.
Damage MODIFIERS
Some objects have a trait that makes them particularly strong against, or vulnerable to, certain damage
types. For example, a Knight may have the Lightning +2 trait, while a Demon might have the Flame -2 trait. If a creature has a trait that modifies a type of Damage, the attacker modifies the number of dice rolled by the value of the trait. Also, if the attack has an additional effect, you add or subtract the modifier to the effect die roll.
I hope this helps.