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Monster Design
Design & Development
by Mike Mearls and Chris Sims

At this year's D&D Experience, R&D's Mike Mearls and Chris Sims presented the following seminar on Monster Design—creating new and custom-tailored creatures for your game. The seminar, as Mike indicated, focused more on powers and roles rather than the mechanics of a monster's stat numbers (AC, defenses, etc.). Here is the information assembled from their presentation and Q&A:

Starting with a Concept

When designing a new monster, you might start with any of the following concepts in mind:

  • A new power or effect you wish to see used by a monster;
  • An encounter or environment you wish to stage for a monster;
  • A visual or cinematic scene where a particular monster is the star;
  • An existing mini that you wish to substitute for a new or different monster.

To take just one example, when Mike designed H2 Thunderspire Labyrinth, he wanted to include a Temple of Vecna. Inside, he envisioned a monster that stole a PC's secrets -- but how?

Expressing the Concept: Powers

Once you have the seed for a new monster in mind, how do you express its abstract concept in game terms? First, consider what expression the concept will have at the table in terms of powers. In the example above (which turned into Encounter T1: Level of Defense), the Enigmas of Vecna used their memory ripper power to limit the PCs to using basic attacks, in essence stealing the secrets of their powers.

Ranged Memory Ripper (standard; at-will) Psychic
Ranged 5; +10 vs. Will; 1d10 + 5 psychic damage, and the target cannot use encounter attack powers, daily attack powers, or utility powers (save ends). Aftereffect: The target is dazed until the end of its next turn.

Another example is the Bugbear Strangler (MM p. 136). It grabs you using strangle, which must then be escaped—requiring a more dynamic action as opposed to making a more passive saving throw to free yourself.

Also consider how powers can be designed to cascade, so that one plays off the next. After the Bugbear Strangler grabs you, it can then protect itself using body shield. Other examples might include monsters that first make PCs vulnerable to fire, then follow up with fire-based powers.

Melee Strangle (standard; sustain standard; at-will)
Requires combat advantage; +9 vs. Reflex; 1d10 + 4 damage, and the target is grabbed (until escape). A target trying to escape the grab takes a –4 penalty to the check. The bugbear strangler can sustain the power as a standard action, dealing 1d10 + 4 damage and maintaining the grab.
Body Shield (immediate interrupt, when targeted by a melee or a ranged attack against AC or Reflex; recharge 456)
The bugbear strangler makes its grabbed victim the target instead. The bugbear strangler can’t use this power to redirect attacks made by a creature it is currently grabbing.

Other options include using recharge abilities to allow your monster's power to be a little more aggressive (it can't be used often, but it might reappear). Powers should make stylistic and thematic sense; e.g., ogres should hit hard, not shift around quickly. Try to create new powers that achieve unexpected results that are still logical, not unexpected results that simply feel false.

Originally, body shield was an opportunity action, meaning it could be used against every potential attack instead of just one, but it also required an attack roll to succeed. That slowed down the game down until the Strangler's target was freed … or slain. The very first 4th Edition PC ever killed, in fact, was done in during an early playtest by a Bugbear Strangler using body shield.

Some powers can be created that are specific to the encounter you have in mind. Monsters might benefit from a nearby altar to Tiamat for instance. Outside the dungeon, it's not as if they'll carry an altar around with them. This can be perfectly fine—you can create monsters and powers for locations in your adventure that will not have general use outside of it.

As a final note, always feel free to create new and change existing powers based on the challenges you wish to present your particular players.

Expressing the Concept: Roles

Next, consider your concept in terms of what monster role it fits best (DMG p. 54). That said, while roles serve as useful categories to help with your design, they are not meant to restrict that design. Some monsters may break roles, depending on how you want it to play (a melee guard, after all, may carry a bow as well).

Taking a look at the various roles, lurkers and controllers may be the most subtle to design—and so, we'll start with them.

Lurkers are meant to remove themselves from battle and away from damage, then gain an advantage upon their return (making a deposit with interest, so to speak). Sneak attacks and invisibility effects are better suited to them than, say, combat advantage, which encourages monsters to stay in the fight. Give your lurkers an excuse (and opportunity) to leave the fight; should their best move be to run away entirely, allow them to run away. Players love to hate lurkers for this reason, which is not necessarily a bad thing. Recurring and hated opponents make good villains.

Controllers are meant to evoke conditions; they are monkey wrenches, either setting up their monster allies (sliding PCs next to skirmishers, for example) or foiling the PCs' actions. While lurkers can drag out a fight, controllers can bring one to an outright halt. Be careful in their encounter composition; three Gnome Arcanists (MM p. 134), for example, can daze an entire party. When it comes to designing your controllers, consider area effect conditions as encounter powers and those that target single opponents as at-will powers. 4th Edition monsters should never run out of tricks, so a controller's basic attack should still include some means of affecting the party.

When it comes to designing brutes, avoid defensive powers and healing (in fact, you'll hear this reiterated). Let the PCs hit them. When your brutes hit back, their average damage should be higher than normal. Roll more dice to achieve this—2d6 instead of 1d12 or 1d6+4. Knocking PCs prone also conveys a brute's powerful hits.

In general, avoid healing powers. Don't allow a fight to turn into a grind. Second wind should be reserved for monsters you wish to have escape. You might instead look at regeneration, which can be shut down by the PCs, or sacrificial abilities where appropriate (for example, a monster might kill its own minions to heal itself, which keeps the current hit point total of the encounter the same but redistributes those hit points where you prefer). On the same note, be careful of insubstantial monsters, because dealing half damage to them is effectively the same as giving them double hit points.

Soldiers should have a similar position as brutes along a survivability timeline, but where brutes have higher hit points, soldiers enjoy higher armor class. You can also have them knock PCs prone in order to keep them close and in the fight.

Skirmishers (as the wild cards) are largely defined by their movement abilities. Design them to threaten the "squishy" PCs (those hanging out in the back) and to frustrate frontline PCs.

When it comes to solo and elite monsters, be careful about giving them healing powers, because healing a percentage of their hit points effectively adds another monster to the fight. Consider their design and use in terms of a story. A solo monster might gain new powers when bloodied, for instance; a dragon fighting in its lair might fall back to different areas during the beginning, middle, and climax of the battle; and, in general, look at using terrain to make encounters even more dramatic (burning buildings, collapsing ceilings, traps) in ways that can benefit the monster or be disabled by the PCs.

The end of the fight need not be the PCs hunting down and slaughtering the lone, standing monster. Give some thought ahead of time to how you'd like the conclusion of the battle to play out. Should the final monster surrender, escape to warn reinforcements, or fall on its own sword? Do you really need to play out the combat in full, or is it sufficient to treat the final monster as a minion that goes down on the next landed shot?

Minions are meant to die quickly, so avoid giving them effects that end with a save; those effects will disappear when the minion does, anway. Existing monsters can be templated as minions if you wish to add them en masse to a gigantic battle; to create red slaad minions, for example (MM p. 238), you might drop their horrid croak power and make leaping pounce an encounter power.

Finally, when designing NPCs, you can take powers straight from character classes to make them feel more like characters, or use class powers for inspiration. Since NPCs are less disposable than monsters, look at powers that show their leadership role and that help keep them around. (Be careful of giving them too much healing, though. Second Wind is more appropriate for NPCs.) In Mike's home campaign, for example, he's created evil Worshippers of Iuz that, when in danger, turn invisible and cast illusionary versions of themselves in the squares they just occupied (while they make good their getaway). Finally, don't overlook elite monsters. They can fairly easily be considered NPCs with a specific name filed off, meaning they're readily modified by you to make suitable villains.

Many thanks to everyone who attended and participated in the seminars at D&D Experience 2009. As an added bonus, those at the seminar were given a chance to win a free pass to Gen Con Indy 2009 (with one attendee at each seminar winning a pass)—our congratulations to the lucky winner!