In my playtest for PF2 last week, after I had three 'normal' encounters, I did one 'test' encounter to try out a Monster Hunter style custom critter. I sorta stitched together three monsters.
It was a large bird - like an axebeak with a bladed peacock tail, wings that could function like shields, and the ability to spit fire. It was basically an ankheg as its 'head' (CR 3) plus a hobgoblin soldier as its 'wings' (CR 1) and a water mephit as its 'tail' (CR 1).
The players scouted its lair, put their ranged attackers up on a ridge, and sent the fighter and bard to lure it into the optimal range. It put up a nice, scary fight, but they were ready for most of its tricks.
They enjoyed breaking its wings, and everyone cringed when the fighter smashed its beak and it started to drool flaming oil, squawking and staggering away with only its tail attack left to fend people off. After it finally fell, everyone took a trophy.
I saw it as a hit. I think this style monster works well given that PF2 already has 3 actions a turn as a default. I wonder if anyone would want to try this out with their party, and see if it might make for a more dynamic fight than current 'big monsters.'
The Guardian Beast of Cemjan Isle
Creature 5 (Animal, Large, Dire 3)
Perception +8; low-light vision
Skills +5; Athletics +9, Intimidation +5 (no penalty for lacking language)
Str +4, Dex +1, Con +3, Int -4, Wis +0, Cha -1
AC 19 (21 with wing shield), TAC 15 (17 with wing shield); Fort +8, Ref +6, Will +5
HP 78 total
Speed 25 feet; wings grant fly 20 feet
Dire 3
A monster with Dire 3 is one creature that functions similar to three distinct creatures. It has three 'body parts' that can be targeted and damaged independently. Each body part can have its own abilities, actions, reactions, and movement modes, and its own HP. The creature's main entry lists its overall skills, ability scores, AC, and saves, which all body parts have unless they note otherwise.
The creature still has one hit point total, and is only defeated once its overall HP is reduced to 0. When a given body part is reduced to 0, excess damage is wasted; it does not carry over. If an attack that affects an area would deal damage to the entire creature's space, it takes that damage to each of its body parts. If the attack doesn't affect the entire space, it only affects one body part of the attacker's choice.
The dire creature gets a number of actions on its turn equal to 2 plus its Dire rating (so 5 for this Guardian Beast), and a number of reactions each round equal to its Dire rating. Each turn it can spend no more than three actions for any single body part. Move actions don’t count as any particular body part’s action, but the creature as a whole can’t move more than three times per turn. It only takes multiple attack penalties if it uses more than one attack action with a single body part.
Whenever a body part is reduced to 0 hit points, that body part is crippled. The creature can no longer use that body part's various abilities, and the total number of actions and reactions it can take per turn are each reduced by 1.
HEAD
The guardian beast’s head boasts an axe-shaped black beak that drips flaming oil.
HP 38
@Action@ Melee beak +9, Damage 1d6+4 piercing plus 1d6 fire
@Action@ Ranged spit fire +6 touch (range 30 feet), Damage 2d6 fire
@Action@@Action@ Armor-Rending Beak The guardian beast makes a beak Strike; if the Strike hits, the target’s armor is dented.
@Action@@Action@ Fiery Squawk (acid)
. . Frequency Once per hour.
. . Effect The guardian beast shrieks and sprays fire in a 30-foot cone, dealing 3d6 fire damage and 1d4 persistent fire damage (Reflex DC 17 half, no damage on a critical success, double damage on a critical failure).
WINGS
The guardian beast’s feathered wings are strong enough to deflect blows.
HP 20
@Action@ Melee wing slice +7, Damage 1d8+2 slashing.
@@Action@@ Ranged hurled feathers +7 (deadly 1d10, range increment 60 feet), Damage 1d6 piercing
@Action@ Wing Shield The guardian beast raises its wings defensively, which grants +2 AC and TAC to the entire creature (not just this body part), and functions as a shield with hardness 3. If it uses this action, it can use a reaction to Shield Block (against an attack that targets any body part). This wing shield can take 3 dents before it breaks. The damage that gets through the shield’s hardness damages whatever body part was originally targeted.
TAIL
The guardian beast’s magnificent tail fans out behind its body, colorful as a peacock but forceful enough to knock a horse flying.
HP 20
@Action@ Melee tail wallop +7, Damage 1d6+1 bludgeoning plus Push 5 feet.
&Reaction& Terrifying Tail Rattle
. . Trigger A creature within 30 feet attacks the guardian beast.
. . Effect The guardian beast makes an Intimidiation check to demoralize that creature.
Three separate creatures would get nine actions, but would spend one or two to move each, leaving three to six left. And generally the reactions of one couldn't protect the others. I feel like 5 is a good compromise, since any move action is sorta doing triple duty.
If there were three separate monsters, killing one doesn't carry over damage to another. And in Monster Hunter, you can accidentally strike the hit box of a body part that's already broken. With these rules you can't do that, so there's no need to have damage carry over.
This is pretty cool! I think you've represented the Monster-Hunter-style mechanics well.
I had an idea to try the same thing in PF1, but I worked from starting with a monster and trying to break it into "parts," instead of having each part be a monster stitched together into one. This works way better and gives the monster more fun abilities.