FREQUENCY: Very rare
FREQUENCY: Very rare ([Dungeon Level VI])
FREQUENCY: Very rare ([Ethereal Plane])
 

NO. APPEARING: 1
ARMOR CLASS: 0 (10)
MOVE: 15"
HIT DICE: 8
% IN LAIR: Nil
TREASURE TYPE: Nil
NO. OF ATTACKS: Nil
DAMAGE/ATTACK: Nil
SPECIAL ATTACKS: Aging
SPECIAL DEFENSES: Semi-ethereal, immune to normal weapons and missiles
MAGIC RESISTANCE: 75%
INTELLIGENCE: High
ALIGNMENT: Lawful evil
SIZE: M
LEVEL/X.P. VALUE: VI | 825 + 10

Misguided research by a high-level illusionist (which led quickly to his
death) created the visions - summoned beings which appear as
shadows. The visions are unable to return to their own plane until
their physical manifestations are destroyed on the Ethereal/Prime Material Plane;
thus they roam the underworld in perpetual frustration
and attack all they meet.

A vision exists partially on the Prime Material Plane and partially on
the Ethereal Plane; if attacked from the material plane they are
treated as AC0. but if attacked ethereally they are AC10.

A vision attacks by suggestion, not by physical means. Anyone seeing
a vision within 30' must roll 3d6, add 3, and compare the result with
his intelligence. If the character's intelligence is the greater, he has
saved and can no longer be threatened by that particular vision. Any
previous 'ageing' he has suffered is seen to have been unreal. A
character failing to save will believe that he has aged ten years (the
effects of aging are covered in AD&D  DMG). Each character seeing a
vision is 'attacked' in the same way and must attempt the special
saving throw, repeating this process each round.
If a character kills a vision, he must make a normal saving throw against
magic; if this is successful, the apparent ageing vanishes, but if not it
is real and permanent.

A vision can only be attacked by magical or silver weapons on either
plane of its existence. The clerical bless spell inflicts 3-18 hit points
of damage on it, while dispel illusion cast on a vision causes 0-5 (d6
minus 1) hit points of damage on it per level of the caster (so a 7th
level illusionist casting this spell on a vision would roll d6 seven times,
subtracting 1 from each roll and adding the results).

by Mike Ferguson