The Wrath of Kings
A character with the controller role primarily handles crowds by creating hazardous terrain and re-positioning enemies, or spreading conditions and damage over multiple enemies. The wizard is the classic controller class.
A character with the defender role primarily focuses enemy fire by making it difficult for enemies to move past, and punishing enemies who attack other party members. The fighter is the classic defender class.
A leader primarily supports the party by aiding allies, and making enemies more vulnerable to attack. The leader role refers only to a class’s combat function; a character with a leader role does not have to be the decision maker or spokesperson for the party. The cleric is the classic leader class.
A striker primarily eliminates single threats by closing with a target quickly and safely, then rapidly dealing damage to it. The rogue is the classic striker class.