I think this was the final version.
Crosod is optimized for stealth and swift, devastating attacks, using haste, expeditious retreat and his quickened spell-like abilities. His maximum double-move – 1200 feet per round when flying – translates to around 140 mph.
When encountered first by Shomei he was hugely buffed – immune to sonics, death warded, invisible and under the protection of mage armour and an unholy aura. His Charisma was 34 – pumping up his Save DCs – and his Constitution was 35 – granting him another +4 on Fort saves and an additional 136 hp. His arcane sight, and detect thoughts were also running and he was surrounded by a zone of revelation.
His ‘official’ CR is 22 – which feels a tad on the low side. The DC 31 save against his destruction was the one which Zhorion failed – the Solar rolled low. Crosod’s high caster level for his spell-like abilities means that he simply ignores SR 35 or less.
The Wyrm Crosod
Shadow Half-Fiend/Half Black Dragon (Wyrm); CR 22; Gargantuan Outsider (Dragon); HD 34d12+272; hp 493; Init +6; Speed 90 ft., fly 300 ft., swim 90 ft.; AC 42 (-4 size, +2 Dex, +37 natural); Attack: +44 melee (bite), +39 melee (claw), +39 melee (wing), +39 melee (tail slap) or +44 melee (crush); Dmg: 4d6+14 (bite), 2d8+7 (claw), 2d6+7 (wing), 2d8+21 (tail slap) or 4d6+21 (crush); SA Breath weapon, frightful presence, fast healing 2, spell-like abilities, spells, snatch; SQ Blindsight, darkvision, evasion, DR 20/+3, immunities, keen senses, shadow blend, SR 26, water breathing; SV Fort +29, Ref +23, Will +25; AL CE; Str 39, Dex 14, Con 27, Int 22, Wis 19, Cha 25.
Crosod’s Charisma includes a +5 inherent bonus.
Skills: Bluff +38, Diplomacy +38, Hide +32, Knowledge (arcana) +37, Knowledge (local, Afqithan) +37, Knowledge (the Planes) +37, Innuendo +35, Intimidate +38, Listen +37, Move Silently +37, Scry +37, Sense Motive +35, Spellcraft +40, Search +37, Spot +41
Feats: Corrupt Breath Weapon, Wingover, Flyby Attack, Quicken Spell-like Ability, Empower Spell-like Ability, Empower Spell, Enlarge Spell, Improved Initiative, Power Attack.
Spells Per Day: 6/8/8/8/7/7/5; Save DC 17 + spell level; 1st level – expeditious retreat, know protections, mage armour, spider climb, true strike; 2nd level – blindness/deafness, detect thoughts, eagle’s splendour, endurance, invisibility; 3rd level – arcane sight, displacement, fireball, haste; 4th level – dimension door, polymorph self, sonic orb, zone of revelation; 5th level – hold monster, Rary’s telepathic bond, sending; 6th Level – acid storm, greater dispelling
Breath Weapon (Su): Every 1d4 rounds, Crosod can breath a line of acid 5 ft. wide and 120 ft. long for 22d4 points of damage (Reflex Save DC 34). Half of the damage dealt by Crosod’s breath is unholy damage.
Frightful Presence (Ex): When Crosod attacks, charges or flies overhead, creatires within 220 ft. with less than 34 HD must make a Will saving throw (DC 34) or become shaken for 4d6 rounds.
Spell-like Abilities: At 13th level (Save DC 17 + spell level): 3/day – darkness (110 ft. radius), insect plague; 1/day - corrupt water, plant growth. At 34th level (Save DC 17 + spell level) : 3/day – darkness, poison, unholy aura; 1/day – cause fear, desecrate, mirror image, plane shift (Plane of Shadow only) unholy blight, contagion, blasphemy, unhallow, horrid wilting, summon monster IX (fiends only), destruction.
Evasion (Ex): If exposed to any effect that normally allows a Reflex saving throw for half damage, Crosod takes no damage on a successful saving throw.
Shadow Blend (Su): In any conditions other than full daylight, Crosod can disappear into the shadows giving him nine-tenths concealment. A daylight spell negates this.
Special Qualities: Acid, sleep, poison and paralysis immunity; cold, electricity and fire resistance 20; darkvision 1100 ft.; blindsight 330 ft.; low-light vision.; +2 luck bonus to saving throws.