Otherwise what's the fun to put a Pit fiend against a 1st level party?
Agreed. And if you're really evil, you could always throw this against a 1st-level party:
[SBLOCK=Enter if you dare]
Ur-Apocalypse Beast (Relentless Apocalyptic Three-Headed Great Wyrm Prismatic Dragon)
Colossal+ Dragon
Hit Dice: 780d12+120120 (129480 hp)
Initiative: +39
Speed: 90 ft, fly 380 ft (clumsy), swim 90 ft
Armour Class: 272 (-8 size +87 natural +78 divine +66 deflection +39 Dex) touch 185, f-f 233
Base Attack/Grapple: +780/+866
Attack: 3 Bites +850 melee (12d6+70)
Full Attack: 3 Bites +452 melee (12d6+70), 2 Claws +450 melee (6d8+35), 2 Wings +450 melee (6d6+35), Tail Slap +450 melee (6d8+105)
Space/Reach: 80 ft./30 ft. (50 ft. with bites)
Special Attacks: Breath Weapons, Ultima Blast, Frightful Presence, Spells, Spell-like Abilities
Special Qualities: DR 260/-, SR 270, Arcane Rejuvenation, Blindsense, Keen Senses, Regeneration, Immunities
Saves: Fort +585, Ref +470, Will +497
Abilities: Str 151, Dex 88, Con 318, Int 142, Wis 143, Cha 142
Challenge Rating: 115
Breath Weapons(Su):
Head 1: 350 foot long cone 240d10 fire or 120 Strength damage
Head 2: 350 foot long cone 240d8 cold or Paralysis for 10d6+120 rounds
Head 3: 700 foot line 240d6 lightning or 350 foot long cone Repulsion for 10d6+120 rounds
Any Head: 10x Prismatic Spray effect (DC 203)
3 Heads: 700 foot long cone 240d12 pure magical energy
Ultima Blast(Su): Once per day, the Apocalypse Beast unleashes a concentrated wave of pure arcane energy. The burst slays all living creatures within a 312,400 ft. (about 59 miles) radius as it infuses them with arcane energy until their overwhelmed bodies are transformed into energy themselves by the massive overflow. A successful Will Save (DC 554) resists the death effect, but targets within range still suffer 78d8 points of damage. Any creature that survives this attack has a 78% chance to gain the Enchanted Template.
Frightful Presence(Ex): All creatures within 1080 ft. who see the Apocalypse Beast attacking, charging, or flying overhead must succeed on a Will Save (DC 466) or become panicked for 24d6 rounds if they have 24 HD or less, or shaken for 24d6 rounds if they have 25-779 HD. Those with 780 or more HD are immune to this effect.
Spells(Sp): The Apocalypse Beast casts spells as a 80th level sorcerer, plus it can choose any spell from the Magic or Spell domain or the druid spell list. Best of all, it has spell slots up to 30th level spells. 0-6 1-23 2-23 3-22 4-22 5-22 6-22 7-21 8-21 9-21 10-16 11-15 12-15 13-15 14-15 15-14 16-14 17-14 18-14 19-13 20-13 21-13 22-13 23-12 24-12 25-12 26-12 27-11 28-11 29-11 30-11
Spell-like Abilities(Sp): At will- All dragon spell-like abilities
Arcane Rejuvenation(Su): Three times per day, the Apocalypse beast can absorb energy from the Weave to regain all lost hit points as a standard action.
Blindsense(Ex): The Apocalypse Beast can pinpoint creatures up to 720 feet away. Opponents the Apocalypse Beast can't actually see still have total concealment against the Apocalypse Beast.
Keen Senses(Ex): The Apocalypse Beast sees 12x as well as a human, and has darkvision out to 1440 ft.
Regeneration (Ex): The Apocalypse Beast regenerates 780 hp per round and takes normal damage from legendary weapons.
Immunities(Ex): The Apocalypse Beast is immune to mind-affecting spells, sleep, stunning, paralysis, disease, light, blindness, death effects, ability drain, acid, cold, electricity, sonic, and fire damage.
[/SBLOCK]