Spells in red are active during combat. I just noted a mistake or two, as well, but it will give you an idea of what they were up against.
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Oathenor, Mature adult half-earth elemental deep dragon: CR 18; Huge Outsider (Earth, Chaotic, Evil); with many spells active.
HD 24d12+216; hp 372;
Init -3;
Spd 40 ft (freedom of movement), fly 90 ft (good) or 150 ft (poor), burrow 20 ft, swim 30 ft;
AC 41/48 (+7 shield, +4 mage armor, -3 Dex, +4 haste, -2 size, +26 natural); + expertise
Melee bite +34 (2d8+12), 2 claws +29 (2d6+6), 2 wings +28 (1d8+6), tail slap +28 (2d6+18); + haste
SA breath weapon, frightful presence, spell-like abilities, true seeing, snake form, humanoid form, half-earth elemental spell-like abilities;
SQ +4 save vs. poison, immunities, cold resistance 10, sonic resistance 5, fire resistance 10 (half damage), acid resistance (half damage), blindsight, keen senses;
DR 50/+3 iron body or 10/+5 (150 stoneskin points max) or 10/+1,
Face/Reach 10 ft by 40 ft / 10 ft;
SR 26;
AL CE;
Saves Fort +21, Ref +11, Will +19;
Abilities Str 35, Dex 5 (normally 8, with cat’s grace and iron body), Con 28, Int 20, Wis 21, Cha 20.
Skills: Bluff +29, Concentration +31, Diplomacy +29, Escape Artist +23, Knowledge (arcana, underdark, history, tasty yummy things) all +29, Listen +29, Scry +29, Search +29, Sense Motive +29, Spellcraft +29, Spot +29;
Feats: Hover, Flyby Attack, Power Attack, Expertise, Improved disarm, Quicken spell-like ability
SA–Breath Weapon (Su): Cone of flesh corroding (acid) gas, 50 feet long, every 1d4 rounds; damage 14d8, Reflex half DC 29.
SA–Frightful Presence (Ex): Dragons can unsettle foes with their mere presence. This ability takes effect automatically (radius 210 ft) whenever the dragon attacks, charges, or flies overhead. A potentially affected creature (one with less than 24 HD) that succeeds at a Will save (DC 27) remains immune to that dragon's frightful presence for one day. On a failure, creatures with 4 or fewer HD become panicked for 4d6 rounds and those with more than 5 HD become shaken for 4d6 rounds.
SA–Spell-Like Abilities: detect magic, true seeing (always active).
SA–Half-Earth Elemental Spell-Like Abilities (at 24th lvl): 1/day-magic stone, soften earth and stone, stone shape, spike stones, wall of stone, earthquake, iron body, elemental swarm*, plane shift.
* Cast as an earth spell only.
Spells Known (cast 6/8/7/5; as a level 7 sorcerer): 0–daze, resistance, detect poison, read magic, dancing lights, ghost sound, mage hand; 1–endure elements, mage armor, shield, true strike, ventriloquism; 2–cat’s grace, endurance, fog cloud; 3–fly, haste
SA–Snake Form (Su): 4/day, this dragon can assume a serpentine form. In this form, the AC drops to 27 and the dragon loses claw attacks, but gains a constriction attack at the same bonus, dealing 3d6+9 damage; this attack has Improved Grab. Speed in this form: 30 ft, fly 20 ft (poor), swim 30 ft.
SA–Humanoid Form (Su): 4/day, shapechange into a basic Humanoid (human, elf, dwarf, hobgoblin, etc.)
SQ–Immunities (Ex): (includes immunities granted by active spells) Immune to charm, disease, earth-based effects, sleep, paralysis, blindness, critical hits, ability score damage, deafness, disease, drowning, electricity, poison, stunning, and all spells or attacks that affect the character's physiology or respiration.
SQ–Blindsight (Ex): Dragons can ascertain creatures by nonvisual means (mostly hearing and scent, but also by noticing vibrations and other environmental clues); this dragon's range is 210 feet.
SQ–Keen Senses (Ex): Dragons can see four times as well as humans in low-light conditions and twice as well in normal light. They also have darkvision (range 700 feet).
Note: Haste only lasts 7 rounds. Already figured in to AC.
