Monster Design Tools: Using Size/Strength as Well as Level

Igor Coura asked a question on Twitter that’s better answered in prose. Igor is in the middle of converting some monsters from other F20 games to 13^th Age, and found himself wondering why we use the category of large monsters to mean “twice as powerful as a normal monster.” Other F20 games tend not to do it that way, when they want a more powerful monster they just use a higher level creature.

13^th Age monster levels determine the important stats that shape every combat: attack bonus, defenses, and hit points. We created the extra-knob for double-strength (and even triple-strength) monsters because we wanted certain monsters to survive longer in a fight, to have more weight as something that the PCs have to take seriously. If you add a couple levels to a monster, it certainly has to be taken more seriously, but as monsters (and PCs) gain +1 attack & defenses each level, the leveled-up monster is also going to be harder to hit and have a much easier time hitting the PCs.

Fighting higher level monsters is certainly one experience. Fighting tough monsters of your own level is another experience. Therefore, when we decided we wanted both experiences in the game, we seized upon the somewhat obvious idea that a bigger creature of a certain level might be tougher than a normal-sized creature of a certain level. Large creatures that are double-the-hit-points-and-damage are part of the story our system is telling. Players can generally count on discovering that large creatures are twice as tough as normal sized creatures, and huge creatures might be three times as tough.

We’ve really liked the impact of having double-strength monsters, so much so that in books after the 13^th Age core rulebook we introduced double-strength creatures that aren’t large. We just wanted to be able to emphasize that a named NPC monster was tougher than the rest, or that a particularly puissant spellcaster or wrecker was going to be twice or three times as much trouble to handle.

We didn’t stop there. 13 TrueWays added weakling monsters, creatures that were only has as tough (hit points and damage) as normal monsters. They’re tougher than mooks, and can’t be killed in batches like mooks, but they’re deliberately not as serious a problem as normal antagonists . . . while still using the attack bonuses and defenses that sit in our game’s sweet spot. That felt right for a couple of the new devils invented by Robin Laws, creatures that have abilities that can be serious campaign problems but their raw combat stats aren’t the point. (Shout out to the honey/slime devil, one of which became the star recurring villain of my 13^th Age Glorantha campaign when reskinned as a Lunar Chaos priestess.)

And speaking of 13^th Age Glorantha, that’s the book where we introduced elite creatures, creatures that are half again as tough as a normal monster of that level. That power level felt exactly right for the Thanatar acolytes—and it’s telling that when I supplied the final hit points/numbers for Ruth Tillman’s similarly spooky jackal priests of the Great Ghoul in 13th Age Bestiary 2(page 123), elite status seemed right. The elite 150% mark is great for extremely dangerous combatants or leaders who you still want to encounter as part of a larger group. Double-strength and large monsters tend to eat up the building-battles possibilities while elite creatures supply some of the same punch while appearing in threatening numbers.

That’s the point of having monsters at different strengths at the same level: to give GMs flexibility when building battles. Well-built battles tell different stories, stories that feel much different when fighting mooks, weaklings, elite, large, or triple-strength enemies. Variable strengths work along with monster-level to provide multiple dials we can adjust each battle and each adventure.