Imagine this scenario: You create a hunter character with random stats and hit points and enter the dungeon to begin exploring for treasure. You stumble upon a zombie pacing near a pile of gear and gold! You attack the zombie and it strikes back! You roll 1D20 and score a critical hit! The 20 point die plus dexterity, against the zombie’s armor class, nets a guaranteed hit. Your damage roll is 1D8 plus your strength and weapon modifier, which is 1D4, more than enough to kill the monster! It falls to the ground motionless. Lying next to the unmoving zombie is leather armor that you pick up.
