The Ass: A Challenge.

[Lord Zentei]

I'm still not sure whether you want a super monster donkey or a realistic one, but if it is the former:

(EDIT: Ninja'd Ah, seems you want an exaggerated realistic one, then. Oh, well...)


Donkey of Doom

Size/Type: Huge Animal
Hit Dice: 13d8+65 (123 hp)
Initiative: +2
Speed: 40 ft. (8 squares)
Armor Class: 16 (-2 size, +8 natural), touch 8, flat-footed 16
Base Attack/Grapple: +9/+27
Attack: Hoof +19 melee (2d6+10)
Full Attack: Slam +19 melee (2d6+10) and 2 hoofs +18 melee (2d6+10)
Space/Reach: 15 ft./10 ft.
Special Attacks: Trample 2d8+15
Special Qualities: Low-light vision, scent
Saves: Fort +13, Ref +10, Will +6
Abilities: Str 30, Dex 14, Con 20, Int 2, Wis 14, Cha 6
Skills: Balance +7, Listen +12, Spot +8
Feats: Alertness, Endurance, Power Attack, Skill Focus (Listen), Run
Environment: Temperate plains
Organization: Solitary
Challenge Rating: 10
Advancement: 13-24 HD (Huge)
Level Adjustment: —

Somewhat more powerful than an elephant.

EDIT 2: since no one else has yet submitted a monster-donkey, I'm adding a couple of traits:

Smell [Ex]

Creatures within 20 ft. of a Donkey of Doom must pass a Fortitude save with DC (10 + ½ the DoD's HD) or become Sickened. This condition lasts for 1d4 turns.

Stubbornness [Ex]

The DoD gains a +4 morale bonus to all mind control effects.


And there you go.

EDIT 3: improved the CR by +1, seems appropos.