These small squirrel-like creatures live in holes dug into the earth. Their sturdy skin can be used to make armor.
Mu (CR 1/2)
N Tiny Animal
Init +3; Senses Low-light vision; Perception +5
AC 15, touch 15, flat-footed 12 (+2 size, +3 dex)
hp 7  (1d8+3)
Fort +2, Ref +5, Will +1
Speed 20 ft., Burrow 10 ft.
Melee Bite +5 (1d4-2)
Space 2.5 ft.; Reach 2.5 ft.
Special Attacks Burrow Attack, Critical Attack
Str 6, Dex 16, Con 10, Int 2, Wis 12, Cha 6
Base Atk +0; CMB -2; CMD 11
Feats Toughness*, Weapon Finesse
Skills Acrobatics +5, Perception +5, Survival +5
Burrow Attack (Ex)
Once per day as a swift action, the mu can come out of the ground and surprise their opponent. If they succeed at hitting with their bite attack, the damage is 1d4-2 plus 1d4 points of earth damage.
Critical Attack (Ex)
Once per day as a standard action, the mu can inflict more pain than normal. If they succeed at hitting with their bite attack, the damage is 1d4-2 x 1.5 for total damage.
The master of a mu familiar gains a +3 bonus on sleight of hand checks.