We have a lot of neat internal tools at Paizo. These include spreadsheets to let us know what parameters new Pathfinder Second Edition monsters should meet to be appropriate for their level. (This information is going to be in the upcoming Gamemastery Guide for everyone to see, although in a table form, not a spreadsheet.) These spreadsheets are fun to manipulate, and my friend James Case is a wizard at such things. He invented a very rough tool to translate monster stats to different levels: put in a Level 3 monster and say you want a Level 5 monster. It looks at, for example, the AC and says, "oh, that's 1 lower than a moderate AC for level 3, here's the AC one lower than a moderate AC for level 5." It does this for most of the monster stats (skills, HP, saves, ability DCs, attacks, damage, and so on), allowing you (with some further review and finesse) to "up level" or "down level" monsters arbitrarily.

Of course, I couldn't help but do ridiculous things with this tool. I made a normal owlbear into a Level 19 creature, and I took the mukradi--a three-headed, energy-breathing bug-goliath--and made it into a little Level 3 creature. That's when I learned the limitations on this numerical translation: these new monsters didn't feel like the right level any more.

An owlbear has a bloodcurdling screech, but it only makes you a little frightened. That's a serious impairment at lower levels, but the highest-level heroes can deal with this so easily it's hardly a challenge. The saving throw DC is really high, as befits a high-level monster, but the effect just doesn't feel serious enough. High level monsters should be more frightening (rules wise) than this: they should be able to scare you to death, not just give you the shivers. Combined with this, the bigger owlbear doesn't have any resistances or immunities to damage, and feels much too straightforward for such a titanic foe. For a Level 19 monster, it's really boring.

Conversely, the mukradi is ridiculously complicated for a Level 3 foe. It has a gajillion different types of attacks, a bunch of complicated defensive abilities, and not just one breath weapon but several. It just feels way, way too complicated for a Level 3 monster. My favorite disconnect, however is this: the mukradi has an awesome, high-level-feeling power called Pull Apart: if it hits you with two of its bites, you have to make a Fortitude save or you die from being torn to pieces. That's pretty epic. On a lower level monster, it seems uncharacteristically vicious, even with the Fortitude DC being reduced to one appropriate for a Level 3 foe. At those levels, you get bleeding wounds or a crippled limb, not "oh, you failed your Fortitude save? Welp, you're dead. Shredded into pieces."

The lesson I took away from this exercise, which I want to share, is to keep in mind that getting your monsters to have the right numbers is only part of good monster design. The other part--and perhaps the biggest part--is that your monster's abilities need to feel appropriate for their level. Benchmark against other similarly-leveled creatures to gauge this. Keep in mind that lower-level monsters shouldn't be super complex (unless they're a main villain or something), and higher-level monsters should be more complex (even if they're just mooks). I see this problem a lot from novice freelancers writing monsters: they pack too much stuff into the low-level monsters, and their high-level monsters are too straightforward.

And, so you can share my delight, here are my two Monsters That Should Not Be:

The Hardly Terrifying OwlbearCreature 19

N, Gargantuan, Animal

Perception +34; low-light vision, scent (imprecise) 30 feet 

Skills Acrobatics +27, Athletics +39, Intimidation +33

Str +11, Dex +4, Con +10, Int –1, Wis +6, Cha +3

AC 43; Fort +34, Ref +27, Will +32

HP 430

Speed 25 feet

Melee [one-action] talon +36 (agile), Damage 3d10+15 piercing plus Grab

Melee [one-action] beak +36, Damage 3d12+15 piercing 

Bloodcurdling Screech [one-action] (auditory, emotion, fear, mental) The owlbear unleashes a loud screech that terrifies its prey. Each creature in an 80-foot emanation must attempt a DC 40 Will save. Regardless of the result, creatures are temporarily immune for 1 minute.

Critical Success The creature is unaffected.

Success The creature is frightened 1.

Failure The creature is frightened 2.

Critical Failure The creature is fleeing for 1 round and frightened 3.

Gnaw [one-action] Requirements The owlbear has a creature grabbed with its talons. EffectThe owlbear attempts to disembowel the creature with a beak Strike. If the Strike hits, the target must attempt a DC 42 Will save.

Critical Success The target is unaffected.

Success The target is sickened 1.

Failure The target is sickened 1 and slowed 1 as long as it remains sickened.

Screeching Advance [two-actions] (auditory, emotion, fear, mental) The owlbear makes a Bloodcurdling Screech and Strides twice. All creatures within 80 feet of the owlbear at any point during this movement are subjected to the effects of Bloodcurdling Screech.

The Littlest Mukradi               Creature 3

N, Large, Beast

Perception +7; darkvision, tremorsense (imprecise) 60 feet 

Skills Athletics +12

Str +5, Dex –1, Con +4, Int –4, Wis +0, Cha –3

AC 19, all-around vision; Fort +14, Ref +6, Will +9

HP 50; Resistances acid 8, electricity 8, fire 8

Partitioned Anatomy [free-action] Trigger The mukradi would be confused, paralyzed, slowed, or stunned. Effect The mukradi confines the debilitating effect to a certain portion of its nervous system, ignoring the effect but causing a maw of its choice to go dormant for the effect’s duration. That maw can’t be used for a Strike or Breath Weapon during that time. This ability can’t be used if all the mukradi’s heads are dormant.

Spitting Rage [reaction] Trigger A creature scores a critical hit on the mukradi. Effect The mukradi’s Breath Weapon recharges. It can use its Breath Weapon immediately as part of this reaction. It can’t use this reaction again until it recharges its Breath Weapon naturally.

Speed 30 feet, burrow 30 feet, climb 30 feet

Melee [one-action] acid maw +14 (magical, reach 10 feet), Damage 1d12+5 piercing plus 2d4 acid

Melee [one-action] flame maw +14 (magical, reach 10 feet), Damage 1d12+5 piercing plus 2d4 fire

Melee [one-action] shock maw +14 (magical, reach 10 feet), Damage 1d12+5 piercing plus 2d4 electricity

Melee [one-action] leg +14 (agile, magical), Damage 2d6+5 piercing

Melee [one-action] tail lash +14 (magical, reach 15 feet), Damage 1d12+7 slashing plus Knockdown

Breath Weapon [two-actions] (evocation, primal) The mukradi breathes a blast of energy from one of its three heads; each creature in the area must attempt a DC 20 basic Reflex save. The mukradi can’t use Breath Weapon again for 1d4 rounds.

• Acid Maw (acid) 10-foot-wide, 30-foot line of acid dealing 4d6 acid damage.

• Flame Maw (fire) 30-foot cone of fire dealing 4d6 fire damage.

• Shock Maw (electricity) 60-foot line of electricity dealing 4d6 electricity damage.

Pull Apart [two-actions] The mukradi makes two Strikes with different maws against the same target. If both hit, the target takes an extra 1d6+5 slashing damage, with a DC 20 basic Fortitude save. On a critical failure, the creature is torn to pieces and dies. The mukradiʼs multiple attack penalty increases only after all the attacks are made. 

Thrash [two-actions] The mukradi Strikes once against each creature in its reach. It can Strike up to once with each maw, once with its tail lash, and any number of times with its legs. Each attack takes a –2 circumstance penalty and counts toward the mukradi's multiple attack penalty, but the multiple attack penalty doesn’t increase until after all the attacks are made. 

Trample [three-actions] Small or smaller, leg, DC 20