A creature I had lying around, converted it over mostly to see how it worked. Since it was based on a REH story, figured it'd be appropriate here ("The Noseless Horror", for the curious).

BOX WIGHT

"When I opened the chest expecting gold and jewels, I didn't understand what I was looking at at first. Then I saw that glassy eye look at me and heard the rattling exhale and I realised it was leathery skin still marked with the signs of torture endured in life, a human body broken and bent into the box. And then it began to... to unfold itself as it pulled itself free of its cramped tomb, each movement accompanied by the popping and cracking of its joints and bones, arms and legs moving in ways a living man could not. Free of its confines it moved jerkily, like a puppet on a string and looked at us, its neck... pop, pop, crack, grind, as it looked at us one by one. Seeing it move so gingerly, we thought perhaps we might have an advantage in speed. But it wasn't slow. It wasn't slow at all." 

Box wights are treasure guardians and traps, the mummified remains of victims who, through a brutal and vile ritual involving a variety of tortures and ritual living mummification, culminating in the body being disarticulated and forced into a too small box. The thick, leathery skin of a box wight is tough, and is almost always marked with the signs of torture. They may be missing noses, fingers (never more than two on each hand, so as not to impede the effectiveness of their deadly claws), ears, jaws, toes, and genitalia, though never the eyes. Box wights remember their tortures and the pain of being put in the box very vividly. Unsurprisingly, for the brief moments they are loosed before they must return to their box, they savagely rip and tear at all living beings that had the misfortune of opening the wrong chest or attempting to make away with sacred treasures. 

Box Wight (Undead Type 7): #E 1d6|AL CE|SZ M|MV 40|DX 10|AC 3|HD 4+3|#A 2/1 (claw/claw)|D 1d6/1d6|SV 15|ML 12|XP 325|TC nil| Special:
Rend: If both claw attacks hit one opponent, rend for an additional 1d8 hp damage.
Immunities: Immune to cold, fear, paralysis, and poison. Immune to mundane weapons; harmed only by silver or magical weapons.
Bound to the Box: Due to their connection to their box, a box wight cannot stray too far from its prison, but is protected in turn by it. While the box is intact, the box wight cannot be turned and receives +2 to all Saves. If the box is destroyed, the box wight will fly into a rage, receiving +2 "to Hit" and Damage and its attack rate increasing to 5/2, tearing apart all living things nearby (even pursuing those that try to flee without treasure) until finally, having no living thing to vent their rage on, they rip themselves apart in a gruesome act of self-destruction. Were an unbound box wight were to make its way out of a dungeon, it might well go on a rampage across the land, killing man and beast alike.* 

*"I've heard of it happening, once. Though sunlight doesn't harm the creature, they despise it and will hide from the sun during the day. A box wight, being so broken and disarticulate, can force itself into spaces that are too small for a normal creature of its size, such as in the gaps of walls, down chimneys, or in the eaves of a house..." -EC