This ability is a key ability to have in almost any deck. It adds X to the amount of damage one of your characters can deal to your opponent without using Fury. (X = The amount printed on the card.)
Kolos of the Nightmare clan is one of the best cards with this ability. His Damage + gives him an additional 6 damage to his base value of 4, making him capable of dealing a whopping 10 damage to an opponent after he wins a fight.
This ability is a game winner in most cases.