You mean Halph, right?
Anyway, the only room earlier in level 13 that requires Halph is along a path that has all green doors; that is, there's no way that you're missing a room along that way because the only way to get to 1N1W is to beat those rooms. You must be missing one in the Southern half of the level, which is fully accessible from where you are. (The ones in the far North you will return to later in the game, after you go down the stairs past the blue door.) Make sure that 1E, 1S1W, 1S, and 1S1E are all complete; with trapdoors it's sometimes hard to see if the room is red on the minimap.
Game on,
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"
He who is certain he knows the ending of things when he is only beginning them is either extremely wise or extremely foolish; no matter which is true, he is certainly an
unhappy man, for he has put a knife in the heart of wonder."
-- Tad Williams
