Mike Mearls sez:

In 4th Edition, your dungeons are going to be a lot more densely populated. The typical encounter has one monster per PC in the party, assuming that the monsters are about the same level as the PCs. An encounter’s total XP value determines its difficulty, allowing you a lot more freedom to mix tougher and weaker monsters. Even better, the difference between a level X monster and a level X + 1 monster is much smaller. You can create an encounter using monsters that are three or four levels above the party without much fear. Add in the rules for minions (which will be described in a future Design & Development article), and you could (in theory) match twenty goblins against a 1st-level party and have a fun, exciting, balanced fight.

This shift in encounter design means a lot for dungeons. With all those monsters running around, you need to give them a fair amount of space for a number of reasons:

• The monsters need to bring their numbers to bear on the party. Wider corridors and rooms allow the monsters to attack as a group. A monster that’s standing around, waiting for the space it needs to make an attack, is wasting its time.
• Multiple avenues of attack make things scary for the PCs and make it easier to get all the monsters into the action. The typical dungeon room where the PCs are on one side of the door and the monsters are on the other grows dull after a while. The PCs kick open the door, form a defensive formation in the doorway, and hack the monsters to pieces. There’s little tactical challenge there.
• Reinforcements need a route to the battle. With more monsters in a fight, you can design dynamic encounters where the orcs in the room next door come barging into the fight to see what’s going on. An extra door or passage in the encounter area is a convenient route for the rest of the encounter’s monsters to show up on the scene. Just because the encounter calls for five orcs doesn’t mean that all five start the encounter in the party’s line of sight.

… So, that’s the first rule of 4th Edition dungeon design. Now that you have more monsters to throw at the party, you can create encounters that spill over greater areas. Opening a door in one area might cause monsters to come from other areas of the dungeon to investigate. With the emphasis switched from one party against one monster to one party against an equal number of foes, you can throw a lot more critters at the PCs.

… Here’s a little homework assignment for all of you: Pick two or three encounter areas on the map and turn them into a single fight.

Dungeon Map

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