When you are engaged in melee combat, strike your opponent to disrupt their concentration, which will allow you to stop them from executing the ability they were about to use.
Abilities are linked to certain classes and can be used by both players and non-player characters (NPCs). To use most abilities, you must first learn them and sometimes invest points into them. Occasionally, you may come across special ability scrolls with a limited number of uses. These scrolls allow you to use the ability even if you have not learned it, but you can only use the ability a certain number of times before the scroll is depleted.