Passageway 4 ends in a locked door. The lock can be picked or forced open with a combined strength of 24.
Inside this small oval shape room, the party finds a collection of treasure.
The lamps (six total) glow with an arcane light (via a continual light spell).
There are all sorts of small chests here (10+1d6) each containing gems (5d8 x 100 gp worth), a decanter of endless water, a spell book with random spells (1d10 1st level, 1d8 2nd level, 1d6 3rd level, 1d4 4th level, and 1 5th level). Despite it's obvious age it appears to be magically preserved.*
*If a player reads a spell from this spell book as if it were a scroll, it will destroy the whole book.
There is a dagger +2, +3 to lycanthropes.
A shield +2, +3 vs. missile fire.
A scroll of teleportation (with detailed descriptions of the 1st level).
As well as 1d4+3 random other magic items.
Three of the small chests act as large bags of holding. A person could carry one each.
There is a jeweled crown (cursed, after possessing it for one year the wearer thinks they are a king and demand to be treated as such).
And a gilded, jeweled dagger. It is sharp but not magical. It is worth 1,000 gp.
Otherwise the room is a dead end.
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Game Masters should reward XP value equal to 1/2 of the GP value of treasure found.