I am beginning to prep for Part 4. In this section there is a Sea Serpent with the Swallow Whole ability.
I'm a little fuzzy on how Toughness works within the Swallow Whole ability. I don't want to make any assumptions on how this ability has worked in previous editions. For this situation, the Sea Serpent has Toughness 18. While in the stomach, if you do more than 18 damage with certain weapons you can get out. What if you do less than 18? Does toughness prevent you from doing any damage? Can you do 18 damage cumulatively over multiple attacks and still get out of the stomach?
As an example, if we assume a 9th level fighter gets swallowed, he will require damage from a light bulk weapon or unarmed attack to deal enough damage to overcome Toughness 18. The issue I see is that the magical weapons that a fighter will have will likely not be light bulk or unarmed. Since damage generally increases due to magic weapons, the fighter will have a hard time doing enough damage to get out of the stomach.
Also note that in this scenario the Sea Serpent is several levels higher and it won't be easy for anyone to escape the stomach any other way. This makes understanding Toughness very important to this encounter.
If anyone has any rules citations they can point to that would be great. Thanks!
Reading Swallow Whole in the Bestiary, we see that Toughness is how much damage the PC needs to inflict to make a hole, but it doesn't say in one blow.
Note that the PC can attack the monster's TAC w/ any unarmed or L-Bulk weapon to do damage to the monster. This is damage as normal (except the PC is Slow 1 & using up their air faster when attacking).
Any slashing or piercing damage done this way also goes toward cutting out, with the target sum being Toughness. Once the damage reaches that number, there's a hole to escape from. The entry also doesn't mention resealing stomachs like many of the PF1 monsters had, so that hole would remain for anybody else swallowed.
While my first impression is that Swallow Whole is kind of weak and most anybody with a magic weapon can cut out in 1-3 rounds, remember that Swallow Whole damage costs the monster no actions and has no failure chance so it's pretty strong already and PCs need to get out fast. Plus they might not have a magic weapon that works. Meanwhile the monster can leave w/ them, sated.
With this encounter, a bite/grab/swallow does 1/3 to 1/2 a target's h.p. before the countdown even starts.
I remember in PF1 having players want to get swallowed because they could do so much more damage inside and were often safer there!
With the See Serpent's Spine Rake 3x/round, that's arguably true here too.