Dragon, Oceanus Ancient (CR 20)

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

AC: 40 (-4 size, +34 natural), touch 6, flat-footed 40
Hit Dice: 34d12+272 (493 hp); DR: 20/magic and 5/evil
Fort +28, Ref +19, Will +23
Speed: 40 ft., fly 150 ft. (poor), swim 90 ft.
Space: 40 ft./15 ft.
Base Attack +34; Grapple +60
Attack: 1 bite +44, 2 claws +39, 2 wings +39, 1 tail slap +39, 1 crush +39, 1 tail sweep +39
Damage: 1 bite 4d6+14, 2 claws 2d8+7, 2 wings 2d6, 1 tail slap 2d8, 1 crush 4d6, 1 tail sweep 2d6
Special Attacks/Actions: Breath weapon 20d8 (35)
Abilities: Str 39, Dex 10, Con 29, Int 18, Wis 19, Cha 18
Special Qualities: Amphibious, immune to electricity, detect evil, control water, smite evil, holy smite, control winds, dispel evil, Frightful Presence: DC 35, SR 35
Feats: #Feats: 12
Skills: Skill points: 142
Advancement: 35-36 HD (Gargantuan)
Climate/Terrain: Any land and underground (Any Upper 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 Oceanus dragon has two types of breath weapon, a line of lightning or a cone of tranquility gas. Creatures within the cone must succeed on a Will save or become dazed for 1d6 rounds plus 1 round per age category of the dragon. Both breath weapons function normally underwater.

Smite Evil (Su): Once per day an Oceanus dragon can make a normal attack to deal extra damage equal to its HD total against an evil foe.

Spell-Like Abilities: At will - detect evil; 3/day - control water, holy smite, water breathing; 1/day - control winds, dispel evil, holy word.

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.