I agree with HeroQuestFrance and Big Bene. Kellar's Keep is intended to be run as consecutive Quests with no trips to the Armory or Alchemist's Shop between. drathe's take is certainly playable, as well. Due to some circumstantial wording, my group had to pause and discuss things in order work-out our own interpretation. Following are some reasons we hit upon:
First, some governing rules of the NA Instruction Booklet from p.23--What Happens Between Quests--tell that the Heroes' BPs, MPs, and spells are restored after they have successfully completed the Quest and have returned safely to the stairway. Finally, Heroes may now visit the Armory. Is there sufficient reason to not allow this in KK?
We found two gameplay differences that we felt disallowed return trips within
Playing Kellar's Keep, p.3: The first difference is that "The Heroes do not start their adventures on the spiral stairway tiles used in the Game System. Instead, they enter through an iron door at the edge of the gameboard." The second difference is that "
Players may leave the gameboard only by locating the wooden exit door (italics mine) on the edge of the board, or by finding the spiral stairway that exists in one of the Quests."
The only exit from a Quest of the Game System Quest Booklet was also the entrance. KK split them so that the only exit from a Quest was now the exit door and
not the entrance door. The result of such a change is that the Heroes are required to follow the Quests in a linked series, always descending deeper and never backtracking to the Armory and Alchemist's Shop.
Or should they be allowed to backtrack? The exit door wording doesn't stipulate that Players may only exit by
passing through the exit, but rather they must
locate it. This is what drathe's point is founded on, I believe. Judging by the stated rules, he is justified in saying visits to the Armory and Alchemist's Shop are allowed after successful Quests.
However, my group felt other thematic elements suggested that KK is a one-way trip down a dwarven interstate with no rest stops or exit ramps. The first is at the end of the introductory narrative passage,
A Message from Mentor: "I shall take you to the Great Gate, but from there you shall be on your own." I believe that
from there you shall be on your own implies not only no returning to Mentor is allowed, but also Armory and Alchemist's Shop visits are out.
The Quests themselves sometimes also provide wording that thematically supports a no-way-back interpretation. Parchment Text from both Quests 5, 6, and 7 state that the Heroes must "escape through the wooden exit door."
More importantly, I think, some of the monster placements before the wooden exit door also make more sense if the Heroes are required to pass through the exit to end a Quest. Otherwise, it is possible to just spot the exit and end the Quest, rather than first defeat the guarding monster(s) to get through the door. This is especially apparent in Quest 6, where 12 monsters that guard the exit can be simply ignored. Even the Guardian of Grin's Crag can be avoided in this way.
[Though this would be odd, as the Guardian must be destroyed to pass the final door and end the Quest Pack. -edit] In my mind, this makes it clear that the Heroes should locate and pass through the wooden exit door in order to end a Quest successfully.
Upon re-reading my post it occurs to me that the Heroes could locate and pass through a wooden exit door and then return all the way back through the previous Quests in order to return to the Armory and Alchemist's Shop. This would be the way to do it while not breaking things with monster avoidance tactics before the exit door. So it's anybody's choice: Just follow the rules as drathe suggests, but modify them by requiring Heroes to pass through the wooden exit door, or follow theme and require the Heroes to play the Quests without return trips.
My group's interpretation certainly restricted our Heroes' progression, but we felt that was the point. Back when we played KK we didn't get resupplied with all those fancy potions and improved equipment...and we liked it!