Ladies and gentlemen... The Freak

The Freak originated during an early, anything-goes phase of my current D&D campaign. He was my buddy Pat's attempt to make a PC that was immune to hit point damage. And he was pretty successful at it, too. The version below is not Pat's grand vision, but rather my attempt to recreate the Freak on a more sound, SRD-based footing. I may make use of him as an NPC at some point. As usual, I did not take updating the skills seriously.

FREAK
(HALF-DRAGON (black) HALF-FIEND TROLL)
Large dragon
Hit Dice: 6d10+50 (83 hp)
Initiative: +4
Speed: 30 ft. (6 squares), Fly 60ft (12 squares), average maneuverability
Armor Class: 23 (–1 size, +4 Dex, +10 natural), touch 13, flat-footed 19
Base Attack/Grapple: +4/+20
Attack: Claw +15melee (1d6+12)
Full Attack: 2 claws +15melee (1d6+12) and bite +10 melee (1d8+8)
Space/Reach: 10 ft./10 ft.
Special Attacks: Rend 2d6+15
Special Qualities: Darkvision 90 ft., low-light vision, regeneration 5, scent, Immunity to poison, acid, sleep, and paralysis, Resistance to cold 10, electricity 10, and fire 10, Damage reduction: 5/magic, Spell Resistance 16
Saves: Fort +13, Ref +6, Will +3
Abilities: Str 35, Dex 18, Con 27, Int 12, Wis 9, Cha 10
Skills: Listen +6, Spot +7
Feats: Alertness, Iron Will, Track
Environment: Cold mountains or Warm marshes
Organization: Solitary or gang (2–4)
Challenge Rating: 9
Treasure: Standard
Alignment: Always chaotic evil
Advancement: By character class
Level Adjustment: +12?

Speaks Common, Giant, Draconic, Abyssal.
COMBAT
Freaks have no fear of death: They launch themselves into combat without hesitation, flailing wildly at the closest opponent. Even when confronted with fire, they try to get around the flames and attack.
Rend (Ex): If a freak hits with both claw attacks, it latches onto the opponent’s body and tears the flesh. This attack automatically deals an additional 2d6+15 points of damage.
Regeneration (Ex): Fire deals normal damage to a freak. If a freak loses a limb or body part, the lost portion regrows in 3d6 minutes. The creature can reattach the severed member instantly by holding it to the stump.
Smite Good (Su): Once per day the creature can make a normal melee attack to deal extra damage equal to its HD (maximum of +20) against a good foe
Spell-like abilities - Darkness 3/day, Desecrate 1/day, Unholy blight 1/day, caster level = HD, Cha-based
Breath Weapon – 60 ft. line of acid. 6d8 damage 1/day. DC 21 reflex save for half.
A freak’s natural weapons are treated as magic weapons for the purpose of overcoming damage reduction.