There are two possible assumptions I see in one aspect of Scarlet Heroes. Damage and monster hit points are scaled down coarsely by 1/4. And a lone PC is roughly 1/4 of an assumed party size. In the context of grognard d&d, a party isn't always assumed to be only 4 or so PCs. B1 3-8 PCs and/or hirelines total. At the risk of coming off poorly, I won't be pulling through my modules for character numbers and levels, especially as some also have an "roughly X total character levels.”. In any case that is one of the assumptions I see, which is probably the best one to use for using SH with newer iterations of D&D, such as Pathfinder, in this specific case Mythic Adventures Pathfinder.
The other possible assumption is that as monsters use d8s for hit dice, they have 4.5 hit points per hit die, so by quartering and chunking damage, those match, with the accompanying side effect of increasing the combat survivability of the lone PC. Since the effect is also that it makes a PC have 4x the normal hitpoints, this is probably an erroneous assumption on my part.
This interrogation of SH came about through the first few sessions of using it with Mythic Adventures Pathfinder, as hit points for everything is much greater, damage is greater, and in particular, my PC Cassondrica does between 1d10+3 to 1d10+9 depending on whether she's using the weapon 2hd and in her armor, as her class the Aegis can boost stats etc when using the psionic armor, and therefore will always do 10 damage on the die is where the table in SH ends, so she does 4 damage just out right. The question being, is this what we want and if not what can we do to change this. Spoiler we've decided to not change anything about for the time being. Which is that we read the stat blocks as per SH, just the total hit die, and that is the monster hp. Otherwise I feel that combat would become the sort of horrible slog we hate in Pathfinder.
Another thing that I noticed on the PC end, is how Challenge Rating, has a big effect on the Fray Die mechanic, which is to say, for level appropriate encounters, Cass can't use the Fray Die we felt was most appropriate as on the whole, monsters/npcs have higher hit dice/levels than the CR. Level X Cass can't use the Fighter's 1d8 Fray Die against CR X monsters. In her case, I asked/suggested that I change it over to the Magic-User's 1d4 Fray Die as she is a psionic character. We haven't had a chance yet to test this. There is also the obvious solution of basing against whom the Fray Die can be used on the CR and not the HD of the monsters. Also, it should be noted that she's made it to level 3 without actually using her Fray Die more than once or twice thanks to the 1d10+9 damage and being able to spread overflow. Which will become less viable as time goes on.
The next thing I've been thinking about is what to do with Mythic Tiers or Ranks. Since Cass hasn't faced any foes with MT or MR, I don't know yet for sure, but I think that simply treating those as additional HD might be sufficient as that is one of the adjustments from MT and MR.
To reference the earlier, and imo incorrect, assumption that damage is quartered because 4.5 hp per HD, I spent some time getting an idea on the hp per HD and CR in Pathfinder, 8 and 15 or so respectively, and did my own damage chart based on dividing damage by 8, my math suggests this a terrible idea, I think. In addition to be work that probably didn't need to be done.
A couple of takeaways. I've had some big sweat "oh fuck is she going to die here" moments despite having more hp than even the average PF PC by virtue of her Mythic Tier. I haven't done near as much combat in that game as all this work and the combat heavy nature of the games involved would suggest, (cue d&d is shitty for basically everything because it's about combat commentary). Because of the close to the SH damage cap she is with her primary weapon, she's still using a 6ft tall statue as a melee weapon instead of upgrading to something with better damage.
I was thinking about adjusting the SH table to have a 3 and 5 damage entry instead of the jump from 2 to 4, or at least some number higher than 5 using the reasoning behind the 0, 1, 2, 4. Possible jumping to either 6 or 8, but I'm unsure as to where to put the breakpoints. This is because of the massive damage Cass can deal and the related, this is supposed to very over the top mythic combat. Or that is my hope with the game I'm playing in.
Currently we're playing through the first installment of the 3pp Adventure Path, Way of the Wicked, but we're talking about transitioning from that to Ultraviolet Grasslands in part because I'm not as stoked about the framing of Way of the Wicked as a solo player. I'd be cooler with playing an evil ap with a group. Don't know why I'm not so keen on it solo, or if it's just how we workshopped Cass's background, she was pulled from Athas with some degree of amnesia and also that Athasians are basically mythic tier creatures when out of the bullshit harshness of Athas.
Because of the nature of the rules combo we're using, I'm about to begin the process of annotating UVG, with ink on the pages, with relevant numbers for PF. The current question is how to translate level and the terse descriptions to PF. The build a monster section in the PF bestiaries are focused on derived attributes by CR. Fortunately, the monster builder in Pathfinder Unchained has HD and CR equal, so I can probably make terse PFUC blocks from the entries in UVG.
