[B0rsuk]

I tend to choose soundtrack by contents rather than track title.

Marignon:
Conquest Of Paradise
Hispanola
(Soundtrack from movie "1492", by Vangelis) Seriously, listen to them and tell me they don't fit.

Diabolical Faith Marignon
Devilred (Moonspell)
Mephisto (Moonspell)

Ermor
Bones of the night
Mortuary
(two above are Planescape:Torment soundtrack by Mark Morgan)

R'lyeh
The official band of R'lyeh is (old) Delerium. Has some really dark and oppressive ambients.
Brainwaves
Sphere
Relics
Rise Above

Iron Faith Ulm
Dungeon Keeper intro (by Mark Morgan, again)
Descent to the Cerberus (Quake 2 music from first level, by otherwise crappy band Sonic Mayhem)

Black Forest Ulm
Julie umira kazdou noc (XIII Stoleti)
Evangelium (XIII Stoleti)
A Poisoned Gift (Moonspell)
Perverse...almost religious (intro) (Moonspell)
Awake (Moonspell)

Pythium
Death Smiles At Us All
The Slave Who Became A Gladiator
Barbarian Horde
(Gladiator soundtrack by Hans Zimmer; can't be beaten here)