Grab a d20. Roll high.
That’s the basic rule of 4th Edition just as it was in 3rd Edition, but the new edition puts that mechanic more solidly in the core of the game than ever.
Ever faced one of those life-or-death saving throws? Hours, weeks, or even years of play can hang in the balance. It all comes down to that one roll. There’s drama in that moment, but it’s drama you didn’t create, and you don’t want.
That’s gone in the new edition.
Have you played a spellcaster and been a little envious of the excitement of other players when they roll critical hits? Have you wished that you could do that for your spells?
You can in 4th.
Have you ever had some confusion or miscalculation about your normal AC versus your touch and flat-footed AC?
You won’t have to worry about it.
If you want to know whether or not you succeed in doing some action in 4th Edition, you grab a d20 and try to roll high. Just as in 3rd Edition, you add a modifier to that roll from your character sheet, and you check for any extra bonuses or penalties from the situation or from your allies. The key difference in the new edition is what you roll for and what you add.
The standard defenses remain (AC, Fortitude, Reflex, and Will) but now they all work more like AC. When a dragon breathes fire on you, it attacks your Reflex and deals half damage if it misses. The DM rolls a d20, adds the dragon’s modifiers, and asks you what your Reflex score is. The dragon might roll a 1 and automatically miss no matter how much tougher it is than you, but there’s also the frightening possibility that it will roll a 20 and deal double damage.
Folks familiar with the new Star Wars Saga system will recognize this concept, but it’s evolved a bit to better suit D&D. In 4th Edition, when a creature only needs to touch you to deliver an attack, it targets your Reflex. When you’re surprised, you grant combat advantage, but you don’t need to look at a special AC on your sheet -- the normal number works fine. When a pit suddenly opens up beneath your feet, you make a check to jump out of danger, but if a crossbow trap fires an arrow at you, it the bolt attacks your AC.
What we mean when we talk about streamlining the system is this: making design decisions that make learning and using the game less difficult, while keeping the system just as robust. And making it more fun as the result.