#3.x

Stuff I know about:

Pathfinder 1e's innovations in 3.x class design. Not useful--class in Infernum is a different concept than in other 3.x games (it's technically a race-as-class system).

PF1e's systematization of "combat maneuvers". I've chosen not to use them because they treat stuff like "tripping" and "disarming" as things that a character would specialize in, rather than options that just Exist.

FantasyCraft (and related games like SpyCraft) Exist and are closely mechanically related to 3.x/d20 modern. I remember reading it once to see if it would be useful for running Eberron. If there's useful mechanical innovation in there, I've forgotten it.

Castles and Crusades (aka the SIEGE engine) and Dungeon Crawl Classics exist. I remember from skimming them that they had more of a 3.x "vibe" than other OSR games, but I think that was more a consequence of their layout and minor stuff like the use of the term "Base Attack Bonus" or "Will/Ref/Fort saves" rather than the actual mechanics

Aye, whenever I say “3.x” I mean basically everything in the 3.0 D&D books from WotC, plus Pathfinder & anything else under that era’s d20 OGL.

(Parenthetically, I have to say that the 3rd Edition D&D books have the best cover designs of any RPG franchise/system/edition ever).

The Sack of Bofa

Allegedly, this overly large, furry belt pouch once belonged to the legendary frost giant Bofa the Synod, a cleric of Thrym of great power to who all other clerics of Thrym deferred to. Though possessed of great magical power, Bofa took particular cruel pleasure in crushing enemies in the two icy boulders he stored in his sack, Blar and Rijm.

It is said that upon his death at the blade of a powerful hero whose name is lost to time, his belt pouch shrank to the size of a large sporran, about the size of the sack you now hold, and indeed, it is cool to the touch, and there are two round objects about the size of small gourds inside, but it seems there is no way to open the pouch, as it is frozen shut and yields to no force or magic. The sack can be hung from the belt by a couple loops near the top, but there is little other notable about the sack.

If worn, the wearer of the Sack of Bofa has their strength increased to that of Bofa (36 in 3.PF, 30 in 5e), but is also more susceptible to critical hits as they are thrown off by the heft of Bofa’s sack (Enemy attacks against the wearer gain +1 critical threat range in 3.PF; enemy attacks against the wearer critical on a 19 or 20 in 5e).

Though the sack cannot be opened, the Sack of Bofa can be wielded as a weapon. In this case, it deals damage as a huge frost sap wielded by a frost giant (2d6+[13 3.PF/10 5e] plus 1d6 cold, Light weapon) and forces a (Will/Wis) save against being frightened (DC 25) for as long as the sack is wielded as a weapon. If the sack is put back on the wearer’s belt and then later taken off to be wielded as a weapon again, anyone in who can see it and has failed a save to it before must make a new save.

While the sack is being wielded as a weapon, the owner does not suffer the increased risk of critical rolls, but also does not have the strength of a frost giant.

5e: Wondrous Item, Very rare, requires attunement

Fun Fact!

Complete Arcane, pg. 119-120; Spell Compendium, pg. 170

“You finger the tiny loop of wire in your hands as you complete the spell. You manipulate the magical aura of the target, creating a damaging feedback reaction, and the target explodes with white sparks.” - Spell Compendium entry

5th-level Abjuration

The target takes 1d6 points of [typeless] damage per spell level of any spell effects currently enchanting it (Will [Wis] save for half). On a failed save, the target is dazed [incapacitated] for 1d6 rounds (Fort [Con] negates). Does not apply to continuous magical effects from equipped magic items.

Layman’s Terms: Target’s enchantments kerplode, maybe disabling the target.

You do this when you’re facing an enemy party and they pile buffs on their warrior -- or, y’know, it’s Ainz Ooal Gown: