Incredibly easy.
Ice Hound
Medium Outsider (Evil, Cold, Extraplanar, Lawful)
Hit Dice: 4d8+4 (22 hp)
Initiative: +5
Speed: 40 ft. (8 squares)
Armor Class: 16 (+1 Dex, +5 natural), touch 11, flat-footed 15
Base Attack/Grapple: +4/+5
Attack: Bite +5 melee (1d8+1 plus 1d6 cold)
Full Attack: Bite +5 melee (1d8+1 plus 1d6 cold)
Space/Reach: 5 ft./5 ft.
Special Attacks: Breath weapon, frosty bite
Special Qualities: Darkvision 60 ft., immunity to cold, scent, vulnerability to fire
Saves: Fort +5, Ref +5, Will +4
Abilities: Str 13, Dex 13, Con 13, Int 6, Wis 10, Cha 6
Skills: Hide +13, Jump +12, Listen +7, Move Silently +13, Spot +7, Survival +7*
Feats: Improved Initiative, Run, TrackB
Environment: Nine Hells of Baator
Organization: Solitary, pair, or pack (5–12)
Challenge Rating: 3
Treasure: None
Alignment: Always lawful evil
Advancement: 5–8 HD (Medium); 9–12 HD (Large)
Level Adjustment: +3 (cohort)
The creature resembles a big, powerfully built dog with short, snow-white fur. Its markings, teeth, and tongue are sooty black. It has blue, glowing eyes.
Ice hounds are relatives of the hell hound and are not originally from the Material Plane. The creatures are summoned to serve as guards in cold weather regions.
A typical ice hound stands 4-1/2 feet high at the shoulder and weighs 120 pounds.
Ice hounds do not speak but understand Infernal.
Combat
Ice hounds are efficient hunters. A favorite pack tactic is to surround prey quietly, then attack with one or two hounds, driving it toward the rest with their frosty breath. If the prey doesn’t run, the pack closes in. Ice hounds track fleeing prey relentlessly.
An ice hound's natural weapons, as well as any weapons it wields, are treated as evil-aligned and lawful-aligned for the purpose of overcoming damage reduction.
Breath Weapon (Su): 10-foot cone, once every 2d4 rounds, damage 2d6 cold, Reflex DC 13 half. The save DC is Constitution-based.
Frosty Bite (Su): An ice hound deals an extra 1d6 points of cold damage every time it bites an opponent, as if its bite were a frost weapon.
Skills: Ice hounds have a +5 racial bonus on Hide and Move Silently checks.
*They also receive a +8 racial bonus on Survival checks when tracking by scent, due to their keen sense of smell.