First off, as I was reviewing Kellar's Keep to see if I missed anything, I noticed the following under the "Components" section regarding Trapdoors:
HeroQuest US Edition Kellar's Keep wrote:Trapdoors
The 2 trap doors are used to link 2 visually unconnected Rooms via an unseen "tunnel." When landing on 1 trap door, a Hero moves instantly to the other trap door.
This is pretty much the only component in KK that has an inbuilt rule to it (even though Quest designers can still easily change this). It deserves to go in the HQ CERB somewhere, probably under the movement section. The rule itself is quite simple - when you land on one trap door, you move immediately to the other. So, all we really need here is a tidy up of the rule to include it after the section about Blocked Square Tiles.
HeroQuest Combined English Edition Rule Book wrote:Trapdoors
The two Trapdoors are used to link two visually unconnected Rooms or Passages via an unseen "tunnel." When a Hero moves onto a Trapdoor, they may move instantly to the other Trapdoor, even if it hasn't been revealed yet.
Passing through a Trapdoor does not require an Action, nor does does it cost any Movement. The Hero can continue their Move from the other Trapdoor as normal.
Heroes cannot see through the Trapdoor, and must travel through the Trapdoor to the other Trapdoor BEFORE they can explore the Room or Passage beyond.
Monsters can NOT move through a Trapdoor.
I think that pretty much covers Trapdoors and how they generally work in the game of HeroQuest.
All this leaves us is the Alchemist's Shop, which works similar to the Armoury and allows the Heroes to buy potions between quests. Four potions are provided. In terms of rules on how to use the Alchemist's Shop and buy potions, we have the following from the KK Quest Book:
HeroQuest US Edition Kellar's Keep wrote:These Potions may only be purchased between Quests.
It's not much of a rule, because it is so simple, so we can include the Alchemist's Shop as an option for Heroes between Quests, as follows:
HeroQuest Combined English Edition Rule Book wrote:Buying Equipment
Heroes may collect valuable Treasures, such as Gold Coins, during a Quest. Between Quests, Heroes may use Gold Coins to purchase powerful Weapons and protective Armour from the Armoury, or potent Potions from the Alchemist's Shop.
The Alchemist's Shop sells Potions, and we already have rules for Potions covered under the Treasure Cards section. As such, it may be an idea to move the rules for using Potions from the Treasure Cards section to the Equipment Cards section, and include a note that Potions from Treasure Cards work exactly like Potions from the Alchemist's Shop. Most of the Potion cards include full details on how to use the Potion, so we can use the Treasure Cards Potions as a means to format the specific Potions from the Alchemist's Shop. From the HQ CERB, we find the following information:
HeroQuest Combined English Edition Rule Book wrote:Potions
Some Treasure cards show Potions. A Hero can either use such a card immediately (returning the card to the bottom of the deck), or keep it and use it later at any time. The Hero should record the Potion on their Character Sheet, and return the card to the bottom of the deck as soon as it is used.
[UK 2nd/US]: The card is discarded. It is not returned to the Treasure card deck.
A Hero may drink a Potion at any time. The way a Potion works and how long its effects last are listed on the Potion Treasure Card, and sometimes in the Quest Book.
A Hero may drink more than one Potion at a time.
Healing Potions are very valuable. If a Hero's Body Points are reduced to zero, they may drink a healing Potion to save themselves before they die, by restoring 1 or more of their Body Points.
A Hero may give one of their Potions to a fellow Hero, but they may do so only on their turn.
From this, we can see that the passages in Bold should be moved, and we can replace them with the following:
HeroQuest Combined English Edition Rule Book wrote:These Potions are used exactly like the Potions from the Equipment Cards deck.
Having done that, it's time to work on the section for Potions under Equipment Cards (which is under the Combat section). It might be worth considering moving the Equipment to it's own chapter in the future, if it gets too big.
HeroQuest Combined English Edition Rule Book wrote:Potions
Some Equipment Cards show Potions. A Hero can keep such a card and use it later at any time. The Hero should record the Potion on their Character Sheet, and return the Potion card to the Equipment Card deck as soon as it is used.
A Hero may drink a Potion at any time. The way a Potion works and how long its effects last are listed on the Potion Equipment Card.
A Hero may drink more than one Potion at a time.
Healing Potions are very valuable. If a Hero's Body Points are reduced to zero, they may drink a healing Potion to save themselves before they die, by restoring 1 or more of their Body Points.
A Hero may give one of their Potions to a fellow Hero, but they may do so only on their turn.
It's worth noting that by making the Potions from the Alchemist'S Shop Equipment Cards, using the Treasure Card rules, that we have created a limit of how many of these Potions may be purchased between Quests in those games where Equipment is strictly limited by the number of Equipment Cards, rather than being written down and returned to the Equipment Card deck. This isn't too much of a problem for us, as multiple copies of these Potions can be handled like multiple copies of Weapons and Armour. Looking over the HQ CERB, I have noted that the rules do NOT specifically state that Equipment is limited by the number of Equipment Cards, as the US rules for the Armoury (which replaced Equipment Cards) has taken precedence here.
Thus, in hindsight, it might be worth looking to see if we should add the limit to Equipment to the number of Equipment Cards available as a UK House Rule, and if so, add another where, like Potion Treasure Cards, Potion Equipment Cards are returned to the Equipment Deck at the end of each Quest, allowing them to be repurchased once again, giving the Heroes some chance of multiple copies of these potions over time, as they could with Treasure Card Potions. The official UK rules didn't have this problem, as the UK version of KK didn't include the Alchemist's Shop (or the addition Artefacts and Spell Scrolls) and thus didn't even consider this issue.
That said, we do already have the UK rule that Treasure Card Potions spoil between Quests, so we can simply expand this to include Equipment Card potions too. Thus, we have two new house rules:
HeroQuest Combined English Edition Rule Book wrote:[UK: All Potions on Equipment cards spoil and must be discarded between Quests.]
HeroQuest Combined English Edition Rule Book wrote:[UK: A Hero may not buy Equipment if there is not a corresponding Equipment Card available in the Equipment Card deck.]
The former is seperate from the same rule for ordinary Treasure Cards, so that groups can decide whether or not to include the rules together. Whilst it may make sense that if an ordinary Potion Treasure Card spoils between quests, that an Potion Equipment Card should also spoil, but the potions are expensive, and some players may feel robbed spending a lot of Gold Coins on a Potion that spoils after a single Quest, thus they may prefer that these cards work more like Potion Artifact Cards, and can be kept between Quests.
The latter is a statement of an implied rule in the UK edition, where you were limited in purchasing Equipment by the number of Equipment Cards available, and many groups used this as a House Rule. Others saw the Equipment Deck as more of a Reference List (like the Monster Cards) and simply ignored this rule. As such, I have added this limit as a House Rule to correct the oversight, but it's not part of the official rules of the HQ CERB.