Dragon, Ethereal Wyrm (CR 18)

Gargantuan Dragon (Extraplanar)
Alignment: Always neutral
Initiative: +0; Senses: blindsense 60 ft., darkvision120 ft., low-light vision, and keen senses
Languages: Draconic

AC: 41 (-4 size, +35 natural), touch 6, flat-footed 41
Hit Dice: 35d12+280 (508 hp)
Fort +26, Ref +19, Will +25
Speed: 60 ft., fly 30 ft. (clumsy)
Space: 40 ft./15 ft.
Base Attack +34; Grapple +56
Attack: 1 bite +40, 2 claws +35, 2 wings +35, 1 tail slap +35, 1 crush +35, 1 tail sweep +35
Damage: 1 bite 4d6+10, 2 claws 2d8+5, 2 wings 2d6, 1 tail slap 2d8, 1 crush 4d6, 1 tail sweep 2d6
Special Attacks/Actions: Breath weapon 22d6 (34)
Abilities: Str 31, Dex 10, Con 25, Int 20, Wis 23, Cha 20
Special Qualities: Immune to ether cyclones, Frightful Presence DC 32, SR 32
Feats: #Feats: 12
Skills: Skill points: 181
Advancement: 35-36 HD (Gargantuan)
Climate/Terrain: Any land and underground (Ethereal Plane)
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): An ethereal dragon has one type of breath weapon: a cone of force. Like all force effects, this breath weapon affects ethereal creatures when the ethereal dragon is on the Material Plane.

Ethereal Vision (Ex): While on the Material Plane, a very young or older ethereal dragon can see ethereal creatures as if they were visible. While on the Ethereal Plane, an ethereal dragon can see normally out to the range of its darkvision (normally, creatures on the Ethereal Plane have a visual limit of 60 feet). Note that blindsense functions normally even on the Ethereal Plane, regardless of visual limits.

See Ethereal (Su): A very young or older ethereal dragon can see ethereal creatures as if they were visible.

Strike Ethereal Creatures (Ex): An ancient or older ethereal dragon can strike ethereal creatures as if they were material. This ability does not allow an ethereal dragon on the Ethereal Plane to affect creatures on the Material Plane.

Extraplanar Subtype

A subtype applied to any creature when it is on a plane other than its native plane. A creature that travels the planes can gain or lose this subtype as it goes from plane to plane. This book assumes that encounters with creatures take place on the Material Plane, and every creature whose native plane is not the Material Plane has the extraplanar subtype (but would not have when on its home plane). An extraplanar creatures usually has a home plane mentioned in its description. These home planes are taken from the Great Wheel cosmology of the D&D game (see Chapter 5 of the Dungeon Master's Guide). If your campaign uses a different cosmology, you will need to assign different home planes to extraplanar creatures.

Creatures not labeled as extraplanar are natives of the Material Plane, and they gain the extraplanar subtype if they leave the Material Plane. No creature has the extraplanar subtype when it is on a transitive plane; the transitive planes in the D&D cosmology are the Astral Plane, the Ethereal Plane, and the Plane of Shadow.