Hit Dice: 24d8+ 144 (252 HP)
Speed: 40 ft. (8 squares)
Armor Class: 23 (-2 size, -1 Dex, +16 natural), touch 7, flat footed 23
Basse Attack/Grapple: +18/+35
Attack: Greatclub +25 melee (3d8+13/19-20) or slam +25 melee (2d6+9)
Full Attack: Greatclub +25/+20/+15 melee (3d8+13/19-20) or 2 slams +25 melee (2d6+9)
Space/Reach: 15 ft./15 ft.
Special Attacks: Trample 2d6+13
Special Qualities: Low-light vision, Darkvision – 60 ft.
Saves: Fort +21, Ref +6, Will +6
Abilities: Str 29, Dex 8, Con 22, Int 6, Wis 8, Cha 6
Skills: +36 Climb
Feats: Ability Focus (Trample), Power Attack, Cleave, Great Cleave, Improved Bull Rush, Awesome Blow, Improved Natural Attack, Great Fortitude, Improved Critical: Greatclub
Organization: Solitary or 1 per 200 Goblins or 1 per 100 Orcs
Challenge Rating: 12
Treasure: 1/10 coins
Alignment: Chaotic Neutral
Advancement: 28 HD (Huge)
Level Adjustment: -
I apologize for the formatting; I typed this up in word, where everything is formatted exactly like in the MM, but the copy job ruined it, and admittedly I'm too lazy to go back through and fix it all. Anyway, for the real point, do you think the CR is appropriate? I realize the hit points seem a tad high, and perhaps the damage too, especially with the trample. I also realize the treasure is absolutely terrible, but that one I'm sure I like. Really I tried to balance the hard hitting and the HP excess with the fact that the Reflex saves and AC are utterly terrible. A mid level spell with a Reflex save has a good chance of owning the thing. Any fighter at 12th level should have no problem hitting with his primary and probably secondary attacks, even his third, if he's properly equipped, has a more than reasonable chance to hit. The other thing is, even enough low to mid level foes could play hit and run for a couple hours and take one down. That said, I'm still not sure if the CR is exactly where it should be. I thought about giving it DR 5/-, but that combined with the masses of hit points seemed excessive. It also takes away the possibility of poking it to death with arrows over a long period of time.
And, sorry for the rambling, but a little background may help you see what I was thinking as I did it. Thanks for any comments. I'll try and answer any questions...if there are any.