Note: Cobolt has the Improved Toughness Feat from The Complete Warrior but all it does is give him 1 extra HP per hit die so you can easily use Cobolt even if you do not have it.
Cobolt CR 8[]
Male human half-blue dragon fighter 6
LE Medium dragon (augmented humanoid)
Init +1; Senses darkvision 60 ft., low-light vision; Listen +1, Spot +1
Languages Common
AC 24, touch 11, flat-footed 23; Dodge
hp 68 (6 HD)
Immune electricity, paralysis, sleep
Fort +8, Ref +3, Will +3
Spd 20 ft. (base 30 ft.)
Melee mwk cold iron heavy flail +13/+8 (1d10+12/19–20)
Base Atk +6; Grp +9
Special Atk breath weapon (line, 6d8 electricity, DC 13)
Atk Options Improved Sunder, Power Attack
Combat Gear potion of resist fire 10, potion of resist acid 10
Str 24, Dex 13, Con 16, Int 12, Wis 12, Cha 10
Feats Cleave (b), Dodge, Great Cleave (b), Improved Sunder, Improved Toughness, Power Attack (b), Weapon Focus (heavy flail), Weapon Specialization (heavy flail)
Skills Intimitate +9, Listen +5, Swim +5
Possessions combat gear, +1 full plate, masterwork cold iron heavy flail