You are right, reading through the first edition rules with an "opening the door moves you through onto the square behind the door" hat on and it seems to me to be as clear as it possibly can be that this is the intent without at any point actually stating it!
You move to the square in front of the door (as The Admiral says that is the only side that you approach it from as you can't pass through a closed door), you can then choose to open or not open the door (and you would have to state this out loud or the evil wizard player wouldn't know), if you choose to open it then the evil wizard player replaces the closed door with an open one, moves your figure through the door into the square on the other side (so that you are now in the room or passageway) and then lays out the contents of the room or passageway.
And, in that edition at least, because you may not move through the same square twice in one move, if you move through a door, you may not pass through it again until your next turn.
So whilst we starting playing the game incorrectly, without this rule, it was pointed out to us by a more experienced player (who I guess now was originally a first edition player) and we played that way ever since, with only a minor tweak in that we counted the "move through the door" as a move (cost one movement point) unless you opened a door with no movement points remaining in which case it was free, but that tweak was just to make counting the squares you had moved easier, you know when you get the frequent situation when someone does the ... no, I started in that square and rolled a seven so one, two, oh yes I do have one move left.
And thank you for that HTML version, it is handy.
And I love these icons


= "special skull" that counts as a "skull" but can be rolled again, once, counting as a normal "skull" if rolled again.
= "skull"
= "shield" cancels out a skull (hero & monster)




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