something I threw together today...
Mezzenbone, Grand Duke of House Mazorgrim, King of Asamet, The Dragon Emperor
Great Wyrm Red Dragon cleric 13 / sorcerer 1
CR 36; XP 78,643,000
CE Colossal dragon (fire)
Init +2; Senses dragon senses, smoke vision; Perception +52
Aura fire (10 ft., 2d6 fire), frightful presence (360 ft., DC 30)
AC 39, touch 0, flat-footed 39 (-2 Dex, +39 natural, -8 size)
hp 679 (29d12+261+13d8+117+1d6+9+43)
Fort +33, Ref +18, Will +34
DR 20/magic; Immune fire, paralysis, sleep; SR 33
Weaknesses Vulnerability to cold
Speed 40 ft., fly 250 ft. (clumsy)
Melee bite +46 (6d6+24/19-20), 2 claws +46 (4d6+16/19-20), 2 wings +44 (2d8+8), tail slap +44 (4d6+24)
Space 30 ft.; Reach 20 ft. (30 ft. with bite)
Special Attacks breath weapon (70-ft. cone, DC 33, 24d10 fire), crush (Large creatures, DC 33, 4d6+24), incinerate, manipulate flames, melt stone, tail sweep (Medium creatures, DC 27, 2d8+24)
Spell-Like Abilities (CL 29th; concentration +35)
At will—detect magic, discern location, find the path, pyrotechnics, suggestion, wall of fire
Spells Known (CL 20th; concentration +26, DC 16 + spell level)
9th (6/day) - soul bind, time stop, weird
8th (6/day) - greater shout, prismatic wall, screen
7th (6/day) - limited wish, mass hold person, spell turning
6th (7/day) - antimagic field, contingency, greater dispel magic
5th (7/day) - sending, telekinesis, teleport, wall of force
4th (7/day) - fear, fire shield, greater invisibility, stoneskin
3rd (7/day) - dispel magic, displacement, haste, tongues
2nd (8/day) - alter self, detect thoughts, misdirection, resist energy, see invisibility
1st (8/day) - alarm, grease, magic missile, shield, true strike
0 (at will) - arcane mark, bleed, light, magehand, mending, message, open/close, prestidigitation, read magic
Unholy Spells (CL 13; concentration +19, DC 16 + spell level)
Domains: Ash, Entropy
7th - destructionD, mass inflict serious wounds, repulsion, word of chaos
6th - geas/quest, harm, harmD, heal, mass inflict...
This isn't how I would have made Ol' Mezzy up, but it's actually done well. Kudos on knowing what you're doing, Randy.