FREQUENCY: Very rare (at best) ([Cold Wilderness Swamp]) <1>
FREQUENCY: Very rare (at best) ([Temperate Wilderness Swamp]) <1>
FREQUENCY: Very rare (at best) ([Tropical Wilderness Swamp]) <1>
FREQUENCY: Very rare ([Dungeon Level VIII])
NO. APPEARING: 1
ARMOR CLASS: Not applicable
MOVE: 12"
HIT DICE: Not applicable
% IN LAIR: Nil
TREASURE TYPE: Nil
NO. OF ATTACKS: Not applicable
DAMAGE/ATTACK: Nil
SPECIAL ATTACKS: Nil
SPECIAL DEFENSES: Normally undetectable
MAGIC RESISTANCE: [SB]
INTELLIGENCE: Animal
ALIGNMENT: Neutral
SIZE: Not applicable
PSIONIC ABILITY: Unknown
    Attack/Defense Modes: Unknown
LEVEL/X.P. VALUE: Not applicable

The trilloch is an energy being from the -NMP- which
lives on the waning life-force of dying creatures and uses its unique
powers to accelerate the process which releases its 'food'. So far as is
known, the creature has no fixed definite form. It cannot be detected
by normal means, though a detect magic spell cast within 60' of the
creature will reveal its distinctive aura and dispel magic within the
same range will drive it away.

So far as is known, no other magic has any effect on a trilloch.
If melee occurs in the presence of a trilloch, detected or othetwise,
all attacks will be at +l hit probability and successful hitswill inflict
+1 damage. The creature can also influence the behaviour of unintelligent
monsters, making them twice as likely to attack a party
encountered.

A trilloch will often stay with a large, powerful monster, thriving on
the huge amounts of life-force released by its victims. If this 'host'
is .killed, the trilloch will attach itself to the victor and stay with him
either until driven off or until another, even more powerful creature,
kills i t s new host, whereupon it will transfer to that creature.

Experience of trilloch behaviour is so limited that it may have yet
other powers, as yet undetected. Certainly no means have yet been
discovered whereby the creature can be harmed, so far as can be
detected.

<1: MM2 just lists them as Very rare>
 

by Mike Ferguson
 

Trillochs: These creatures, first described in the FIEND FOLIO tome,
originated in a demi-plane with a high percentage
of negative energy in its make-up. The demi-plane later drifted
too close to the Border Ethereal of the Negative Material plane
and was consumed. Trillochs, the energy vultures of this demi-plane,
managed to thrive in the Negative Material plane.

- Manual of the Planes