It would be interesting to see a list of "rule clarifications" from AH that are not actually printed in any of the boxes (or else is only found in a single expansion).
Helmet is considered "metal" armor and the Hand Axe may not be used by the Wizard (clarified in the "slim box" printing of the retail game system released in January 2022, so owners of the Haslab version and retail owners who purchased the "big box" version released in October 2021 would be unaware of this change until perhaps seeing it again in "Rise of the Dread Moon" expansion where the cards are clarified).
Digital release: Into the Northlands clarifies Polar Warbear double attacks, recovery from Shock, Yeti hugs during solo quests, ice tunnels landing on top of another character, unthreatened movement option, animal companions for solo heroes.
HeroQuest Board Game Companion App (v1.82): New mechanic for escaping a Yeti hug attack if the option is toggled on (roll 2d6, any 5 or 6 is an escape, also the hold can be broken by simply tapping a button), optional Advanced Goblins (move, attack, do rest of movement), Advanced Skeletons (diagonal attacks), add 1 body point, mind point, defend die, attack die to all monsters and double Wandering Monster options. Intangible furniture option (likely for debugging). Polar Warbear double attack allows victim to pick which of the attacks they defend against while the other is unblockable. Guardian Knight abilities can be used in corridors even if the card just says "in the same room." Mage of the Mirror items (Artifacts, Equipment, Treasures) are strictly enforced: if it says "the Elf" then it is ONLY the Elf even if it lacks the wording "may only be used by the Elf." It also enforces the way the "magical darkness" works in the Forsaken Tunnels of Xor Xel which is itself a digital quest. The Elf may choose the Elf Spells in other adventures not just the Mage of the Mirror (even the Game System), instead of one of the Elemental spell groups. The Druid hero was a mythic tier exclusive with no retail version released yet but until fairly recently, the old playtest pages showed all of her cards and the Companion App did as well, while the former pages have disappeared (archived versions can be dug up) and the Companion App has obscured some of the cards, as if a retail re-release were imminent (but those who haven't otherwise recorded that information may be left guessing how to properly play this character).
Oddities from the Companion App that are more likely to be glitches, errata or due to software limitations rather than intentional rule adjustments like searching multiple corridors at once when at a crossroads.... can't search a room or corridor if you have direct line of sight to a monster through the doorway unless it's a secret door, and all characters can pass through Treasure chests, Bard starts with a dagger, Sir Ragnar prisoner can only move two squares on his turn though this rule isn't enforced. You can't walk through a doorway if there's a hero standing in the doorway (he has to move out of the way first). You also can't use Pass Through Rock (or equivalents) to move through a Fallen Block and "Elven Cloak of Passage" only passes through walls and doors but not blocks of any kind. The Frozen Horror monster takes up four squares when moving and attacking but he can also huddle up next to a hero in a corridor as if he's a single square monster (with his icon overlapping) to attack. Specter monsters can land ON TOP of a hero to attack them and pass into unvisited areas. Allegedly monsters with ranged or diagonal abilities are able to attack heroes through walls. Also the "Ancient Staff" artifact only reverses a Dread spell back against the spell caster, while the card says it should also target all monsters in the same room. The Rescue of Sir Ragnar abruptly ends in victory the instant the prisoner hits the staircase when the booklet assumes a quest is only over when the last surviving hero leaves the quest. The 2nd quest of Rise of the Dread Moon ends the instant one hero enters the Hideout (from a door that won't open despite having the key) instead of when the last surviving hero does.
Worth mentioning the Companion app makes other adjustments like adding storyline bits and images not found in the booklets and declares that you can't visit shops after Quest 2 of Rise of the Dread Moon (despite that text being missing from the physical or PDF quest book).
Physical release in retail, but not all will have it: Hero Collection II: Rogue Heir of Elethorn clarifies multi-attacks done by heroes AND monsters (not just done by the Rogue) on its lore card. This suggests it could be retroactively applied back into the Game System in which Heroic Brew and Orc's Bane could give opportunities to hit the same target twice in one turn.
Spell Scrolls throughout the many releases (other than Spirit Queen's Torment and Prophecy of Telor retail releases) lack the words "may be used once by any hero" but it is clarified inside the Rise of the Dread Moon booklet that this is the case for all Spell Scrolls. Spells crumbled to dust after use and they don't have to be used only by heroes who otherwise begin with spells.
Clarifications from social media:
If you a hero can see a monster in a corridor, then any monsters standing behind that monster are not hidden, they are also placed on the board even if a character can't "shoot through them" due to obstructed line of sight.
Crossbow can hit the four close diagonal squares surrounding a character using it ("orthogonal adjacent") just not the four cardinal direction adjacent squares (and of course it can always hit squares that are at range so long as there is unobstructed line of sight).
Shields are not metal and can't be rusted but helmets are made of metal and can be rusted. Helmets are considered to be "metal armor" and Bracers (though not metal) are considered to be "body armor." When a card says "armor" without other clarifications it is assumed to be "body armor" like Chainmail or Platemail. This impacts expansion heroes: Druid, Bard and Rogue (I don't list the Monk, Warlock or Wizard because they don't make references to metal).
The Orc Bard hero, despite his card saying "2" for his defend dice, actually has 3. This bonus doesn't go away if he puts on Bracers (or a magical cloak which is not considered "armor" even though protective) but it does go away if he puts on a helmet, shield, or other types of body armor (and just gives him the defense of those things).
The Warlock hero can only use the spells she starts with (or Spell Scrolls she is given) not the Elemental Spells. This should be obvious from the cards, but people asked so they clarified it.
The Wandering Monk hero's base attack is "unarmed" and thus 2, despite the card and mini may show the character with a weapon in hand. The Monk's base defense is 3, so adding bracers would make it 4, etc.
With regard to Mercenaries they are to be treated like Heroes in most situations. The intention is to be on what it says they can do but also what it doesn't say about them. When in doubt, treat them like a hero (implying you can hand them a piece of equipment and they can use it), disregarding what it says in expansions that haven't been remade (yet). So far there are three types of Mercenaries... the Animal Companion for Into the Northlands (which has more limitations on what it can and can't do) that could be used in other parts of the Frozen Horror campaign or even other solo quests... the Frozen Horror human mercenaries that can be hired in group quests of Mage of the Mirror as well (and may also appear as evil characters in the Frozen Horror at times)... and the Rise of the Dread Moon's Elven mercenaries that are for use in that pack's group quests but could also be purchased for hire in the Mage of the Mirror group quests in theory. Other types of NPCs exist but some of them are not able to fight (Sir Ragnar, Elven Prospector, etc) or are only available for a limited space (usually a quest or two) like the Orc allies in Spirit Queen's Torment.
The Alchemist Deck of potions with gold values (from Rise of the Dread Moon) can be substituted by Zargon into other expansions if he wishes (although only one Potion has a lowered price, there are several that are usable by all heroes rather than just one) when shopping at those Alchemist Shops.
Did I miss any?
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