Ethereal Filcher (CR 3)

Medium Aberration
Alignment: Usually neutral
Initiative: +8 (+4 Dex, +4 Improved Initiative); Senses: darkvision 60 ft., Listen +9, and Spot +9
Languages: Does not speak

AC: 17 (+4 Dex, +3 natural), touch 14, flat-footed 13
Hit Dice: 5d8 (22 hp)
Fort +1, Ref +5, Will +5
Speed: 40 ft.
Space: 5 ft./5 ft.
Base Attack +3; Grapple +3
Attack: Bite +3 melee
Full Attack: Bite +3 melee
Damage: Bite 1d4
Special Attacks/Actions: -
Abilities: Str 10, Dex 18, Con 11, Int 7, Wis 12, Cha 10
Special Qualities: Ethereal jaunt, detect magic
Feats: Dodge; Improved Initiative
Skills: Listen +9, Sleight of Hand +12, and Spot +9
Advancement: 6-7 HD (Medium-size); 8-15 HD (Large)
Climate/Terrain: Any land and underground
Organization: Solitary
Treasure/Possessions: No coins; standard goods; double items

Source: Monster Manual

An ethereal filcher lurks on the Ethereal Plane waiting for a likely mark. Upon locating one, it shifts to the Material Plane, attempting to catch its victim unawares. The creature attempts to snatch an item, then retreats quickly back to the Ethereal. It is not above delivering a bite to distract its target. Once it secures a trinket, it scurries back to its lair to admire its prize. When badly wounded, the filcher escapes rather than continue the fight.

Any number of simple ruses can blunt a filcher's attack. Quick thinking individuals often can recover a stolen item simply by snatching it back before the filcher can escape. Others keep a few cheap baubles available for the local filcher to snatch. Filchers are known to have noses for magic, so items enchanted with Nystul's magic aura or continual flame spells often prove irresistible, especially if they also are gaudy. Fortunately, a filcher usually is satisfied with a single prize.

Ethereal Jaunt (Su): An ethereal filcher can shift from the Ethereal to the Material Plane as part of any move action and shift back again as a free action. It can remain on the Ethereal Plane for 1 round before returning to the Material. The ability is otherwise identical with ethereal jaunt cast by a 15th-level sorcerer.

Detect Magic (Su): Ethereal filchers continuously detect magic as the spell cast by a 5th-level sorcerer. A filcher can suppress or restart the ability once per round as a free action.