<g=4>

FREQUENCY: Unique (very rare)
FREQUENCY: Very rare ([Dungeon Level X])
FREQUENCY: Very rare ([Astral Plane])

NO. APPEARING: 1 <(+ 400-4000 bone devils, in lair)>
ARMOR CLASS: -2
MOVE: 18"
HIT DICE: 126 hit points
% IN LAIR: 60%
TREASURE TYPE: [G], [P]
NO. OF ATTACKS: 1 and 1
DAMAGE/ATTACK: By weapon type +7 / 3-12
SPECIAL ATTACKS: [SB]
SPECIAL DEFENSES: [SB]
MAGIC RESISTANCE: 70%
INTELLIGENCE: Genius
ALIGNMENT: Lawful evil
SIZE: L (9' tall)
PSIONIC ABILITY: 229
    Attack/Defense Modes: All / all
LEVEL/X.P. VALUE: X | 30,000 (material form only)

Amon is a vassal of [Geryon],
mustering and commanding up to 40 companies of bone devils recruited from his fief. <approx. 4000 bone devils - see devil>
He is large and strong, <note exact Str, and link>
typically attacking with a huge +3 mace and delivering a vicious bite as well. <what kind of mace? horseman? footman? the original art (not MM2) shows Amon as being without feet>
He has a [winter wolf] of the largest size as a companion and guardian.
    This creature has +3 to hit and +3 to damage and is 25% magic resistant.
    <stat block, The Wolf of Amon (?), could be appended>

One at a time,
at will,
1 per turn or melee round,
Amon can use the following spell-like powers as a 20th-level magic-user:
    [animate dead],
    [charm monster],
    [detect magic],
    [detect invisible], <link: detect invisibility> <'rename' the spell?>
    [dispel magic],
    [fly],
    [geas],
    [know alignment],
    [polymorph self],
    [produce flame],
    [read languages], <link: comprehend languages> <'rename' the spell?>
    [read magic],
    [suggestion],
    [teleportation], <link: teleport?> <if Arch-Devils are Lesser Gods, then are Dukes of Hell Quasi-Deities?>
    [wall of ice],
    fulfill another's [limited wish].
<which are 1 per turn and which are 1 per melee round? as a suggestion, level 0-4 = 1 per round, level 5-9 = 1 per turn. make 2 separate lists, then : a 'round' list, and a 'turn' list>

Amon causes [fear] in any individuals he gazes upon,
unless they make a saving throw versus spells.
<space>

Once per day Amon can use a symbol of hopelessness. <make direct link>

He can summon, with a 60% chance of success:
    1-4 bone devils.
<slight format change>
<space>

Amon is able to regenerate from 1-12 points of damage per turn.
On the [Prime Material Plane],
Amon can summon and control all wolves within 1 mile of him. <normal wolves, or all wolves in general? I would go with the former>
Amon is wolf-headed but otherwise appears [human].
His torso is well-formed and muscled.