This creature was made using an Orc/Rhino Tauric Monster Of Legend to mimic the Dragon Ogre, a creature from Games Workshop's Warhammer universe, in a D20 setting. The creature is supposed to be an ancient beast, and thusly applying additional class levels onto it to kick it's CR up wouldn't be a bad thing.
Tauric and Monster of Legend appear in Monster Manual 2. The Dragon Ogre also has the feat "Centaur Charge" from Races of the Wild: this is easilly switched with a core rules feat (such as Cleave) if you desire.
Large Outsider (Native)
Hit Dice: 9d8 + 90 (130 hp)
Initiative: +7 (+3 Dex, +4 Improved Initiative)
Speed: 30 ft. (6 squares)
Armor Class: 27 (+3 studded leather armor, +12 natural, -1 size, +3 Dex), touch 12, flat-footed 24
Base Attack/Grapple: +9/+26
Attack: Large Greatclub +22 melee (2d8+13) or Hoof + 22 melee (1d8+13*)
Full Attack: Large Greatclub +22 melee (2d8+13) and 2 Hoof +20 melee (1d8+13*)
Space/Reach: 10 ft./5 ft.
Special Attacks: Lightning Control
Special Qualities: Darkvision 60 ft., immunities, light sensitivity
Saves: Fort +15, Ref +12, Will +8
Abilities: Str 36, Dex 16, Con 31, Int 10, Wis 9, Cha 10
Skills: Intimidate +9, Listen +4, Spot +4, Survival +5
Feats: Centaur Charge (From Races Of The Wild), Improved Initiatve, Improved Overrun, Multiattack, Power Attack
Environment: Temperate hills
Organization: Solitary, pack (3–8) or herd (10–30 plus 150% noncombatants plus 2 4th-level riders per 10 adults and 1 6th-level warlord)
Challenge Rating: 7
Alignment: Often chaotic evil
Advancement: By character class
Ancient, foul-tempered creatures of darkness, Dragon Ogres are rarely roused from their long slumbers, but when the right foul incantations are carried out they will awake once again to ride out and conquer.
Dragon ogres look slightly akin to centaurs, but are far more terrible looking. Their human section is a large, muscled human, with low foreheads and large protruding teeth; their lower body akin to a rhino They are usually 4 to 10 feet long, 7 to 9 feet high at the shoulder, and weighs up to 6,000 pounds. Females are slightly smaller.
Dragon Ogres get only larger with age, however, and legends tell of large herds being led by giant, 30 foot tall warmasters whose lower body was more akin to a lizard. (It is these legends from whence their name seems to come.)
Dragon Ogres speak their own tongue and Giant.
Dragon Ogres are enormously strong beasts, often found as the “heavy hitter” behind demonic cults and other such forces of the damned. They use their bulk as a weapon, over ramming their foes over and trampling them underfoot.
Lightning Control (Su): Once every 1d4 rounds, a Dragon Ogre can use a breath weapon, which has a 15-ft cone area of effect and deals 3d6 electricity damage. (Reflex DC 24 for half)
Immunities (Ex): Dragon Ogres are immune to electricity and fear effects.
Light Sensitivity (Ex): Dragon Ogres are dazzled in bright sunlight or within the radius of a daylight spell.
Centaur Charge: If a Dragon Ogre attempts to overrun a foe, that foe may not choose to avoid them. The Dragon Ogre may make a hoof attack versus any target it knocks down, with the target taking a -4 to AC due to being prone.