Dragon, Shadow Old (CR 18)

Huge Dragon
Alignment: Always chaotic evil
Initiative: +0; Senses: blindsense 60 ft., darkvision120 ft., low-light vision, and keen senses
Languages: Draconic

AC: 36 (-2 size, +28 natural), touch 8, flat-footed 36
Hit Dice: 25d12+125 (287 hp); DR: 10/magic
Fort +19, Ref +14, Will +21
Speed: 80 ft., fly 150 ft. (poor)
Space: 20 ft./10 ft.
Base Attack +25; Grapple +41
Attack: 1 bite +31, 2 claws +26, 2 wings +26, 1 tail slap +26, 1 crush +26
Damage: 1 bite 2d8+8, 2 claws 2d6+4, 2 wings 1d8, 1 tail slap 2d6, 1 crush 2d8
Special Attacks/Actions: Breath weapon 5(DC 29)
Abilities: Str 27, Dex 10, Con 21, Int 24, Wis 24, Cha 25
Special Qualities: Energy drain immunity, Shadow blend, Mirror Image, Dimension door, Nondetection, Frightful Presence DC29, SR 27
Feats: #Feats: 9
Skills: Skill points: 181
Advancement: 26-27 HD (Huge)
Climate/Terrain: Underground
Organization: Solitary (1 dragon, any age), clutch (1d4+1 wyrmlings, very young, young, juvenile, or young adults), family (pair of mature adults and 1d4+1 offspring)
Treasure/Possessions: Triple Standard

Source: Draconomicon

Breath Weapon (Su): A shadow dragons breath weapon is a cone of billowing, smoky shadows with an energy drain effect. Creatures within the cone gain 5 negative levels: the saving throw to remove the negative level is 29. A successful Reflex save (DC 29) reduces the number of negative levels by half (round down).

Shadow Blend (Su): During any conditions other than full daylight, a shadow dragon can disappear into the shadows, giving it nine-tenths concealment. Artificial illumination, even a light or continual flame spell, does not negate this ability. A daylight spell, however, will.