There are multiple ways to complete a lot of the major puzzles, such that you should be able to get at least one of the "neutral" endings. However, if you are having trouble finding all of the thirteen treasures, you may want to consult this list. The bracketed text is what you need to do to get the item, in ROT13 (rot13.com to convert to plain text).

Horse statue [Tvir gur eht gb gur nagvdhnevna, naq fur'yy yrg lbh gnxr vg.]
Amber [Uryc gur nepunrbybtvfg qvt vagb gur grzcyr. Vg'f va gur fvqr-ebbz.]
Bezoar [Chg gur cvyyf vafvqr gur ehoorel yhzcf naq tvir gurz gb gur qrre zbafgre.]
Brass ring [Hfr gur gbjry gb pyrna gur yhzcl bowrpg lbh svaq va gur jrfg onaxf bs gur fgbyra evire.]
Jeweled sword [Svaq vg va gur jvar pryyne, npprffvoyr ol oernxvat gur penpx va gur jnyy jvgu n cvpxnkr.]
Solacefruit [Trg vg sebz gur fuval gerr va gur ynaq-oruvaq-zveebef, gjb ebbzf abegu bs gur nzore jbbqf.]
Ivory key [Cynl gur pbeerpg frdhrapr bs abgrf va gur pnfgyr va gur ynaq-oruvaq-zveebef. Gur pnfgyr vf ebhtuyl abegujrfg bs gur nzore jbbqf.]
Catspaw [Qvr naq orng gur obngzna ng purff. Lbh znl jnag gb purpx gur yvoenel vs lbh'er univat gebhoyr jvaavat.]
Heartmetal [Sbhaq va gur pnfxrg va gur furys va gur ryringbe funsg rnfg bs Crafgbpx'f Jvpxrg.]
Shard [Chg ynper naq lbhe ung va n cnvy gbtrgure naq jnvg.]
Gold brick [Hfr gur oenff xrl, sbhaq va Crafgbpx'f Jvpxrg, gb ragre gur ubhfr ba Zbybpu Fgerrg naq zbir gur cnvagvat.]
Bookmark [Lbh pna svaq vg nsgre ernqvat gur unaqjevggra obbx be tvivat vg njnl.]
Comb [Pbzcyrgr gur evghny va gur cnivyvba. Lbh zvtug jnag gb purpx gur yvoenel sbe zber qrgnvyf.]

If you're stuck, check out the maps included in the download of the game.

Also, because a lot of people had trouble with this - here is a translation of the rules for winning at chess: 
[1. Vs lbhe bccbarag cynlf n pvepyr, cynl n syvag.
2. Vs lbhe bccbarag zbirf n ovfubc be ebbx, zbir n pngfcnj.
3. Vs lbhe bccbarag zbirf vagb O, zbir vagb N. Vs lbhe bccbarag zbirf vagb P, zbir vagb O. 
4. Vs lbhe bccbarag zbirf n pngfcnj, zbir vagb n 1. 
5. Vs abar bs gur nobir ehyrf nccyl, zbir abegu bss gur rqtr bs gur obneq. (N erny purff obneq bayl unf 8 fdhnerf. Zbir vagb fdhner 9.)]




If that's not enough for you, and you're finding the built in hint system unhelpful, you can also consult this playthrough. Note that this is by no means the only way to complete the game.

examine paper
drink tea
[any key]
[any key]
get fedora
yes
get towel
get mirror
read note
w
sw
e
e
talk to Mr. Pages
ask pages about entity
a third dimension
a task
a lair
examine theoretical location of a hideout
a reward
w
get lamp
ask antiquarian about horse
w
sw
s
talk to archaeologist
a crew
get pick
dig chunk with pick
again
again
s
w
get amber
e
n
n
w
get rug
e
n
e
give rug to antiquarian
get horse statue
w
ne
n
n
n
get samples
get oil
s
w
get pills
put pills in lumps
give lumps to deer
z
z
get bezoar
e
e
examine sign
move curtain
talk to scruffy-looking square
a mirror
a land-behind-mirrors
give mirror to square
get mirror
examine mirror
enter mirror
[any key]
n
n
examine tree
get solacefruit
get sap
s
w
nw
n
w
talk to heptagon
a predicament
a escape
give mirror to heptagon
examine mirror
e
s
n
e
play aaaaaa
play bbbbbb
... *the actual correct combination is randomly generated*
play cabeac
get key
w
s
enter mirror
[any key]
w
n
w
n
drop fruit
n
x books
w
x books
get cults
w
x books
e
e
e
x books
get chess handbook
get fire
e
x books
get map
e
get card
w
w
w
s
get fruit
s
w
w
w
w
w
talk to pentagon
a career
a compendium
give fire to pentagon
talk to pentagon
give library card to pentagon
examine device
examine sharp stone
attach flint to device
e
e
e
e
e
s
w
n
w
s
dig crack with pick
e
n
put oil in lamp, light lamp with lighter OR put sap in lamp
get sword
w
n
e
e
s
w
get lumpy object
clean object with towel
drop towel
s
z
z
[any key]
read chess handbook
talk to boatman
yes
1
3
2
3 *the correct moves here are also randomly generated*
n
n
e
s
talk to triangle
triangle, follow me
n
sw
s
s
n
n
ne
s
e
get key
e
pull lever
examine shelf
z
exit
examine foam
e
get pail
examine altar
read writing
put lacre in pail
put hat in pail
z
z
z
z
z
look
get shard
w
n
n
examine casket
open casket
get heartmetal
s
s
e
s
go south until you reach the tunnel entrance OR go south for a while from the wine cellar
examine looking glass OR read maze map
s
s
e
ne
w
se
w
e
e
get chair
examine desk
open drawers
get book
look
examine entity
talk to entity
a book
a regrets
a third dimension
a footsteps
a bats
a pages
a letter
read book
examine bookmark
w
w
n
n
enter mirror
[any key]
enter mirror
[any key]
w
sw
e
e
give chair to pages *optional
give handwritten book to pages *also optional
w
w
s
w
s
s
s
s
get bell
read cults and rituals a history
get instructions
read instructions
light candles with lighter
ring bell
read incantation
[any key]
look
talk to occultist
a cult
z
z
z
z
e
n
ne
n
unlock door with brass key
e
move painting
look
get brick
w
s
e
open case
put brick and comb and heartmetal and shard and catspaw in case
put ring and sword and fruit and key in case
put bezoar and horse and amber in case
put bookmark in case
look
examine sigil
go up
go up
yes
[any key]
***The end***