Doppelgängers are strange beings that are able to take on the forms of those they encounter, including the appearance of equipment and any clothing the victim is wearing. A doppelgänger can assume any humanoid form between 4-ft to 8-ft tall, but the creature must first see the victim to be copied. Any doppelgänger’s attempt at physical disguise is only faulty 10% of the time, and its knowledge of the victim is facilitated by the doppelgänger’s innate ESP ability. In its natural form, a doppelgänger is a 5-ft to 6-ft tall humanoid, slender with gangly limbs and half-formed features. Its flesh is pale and hairless, and its large, bulging eyes are yellow with slitted pupils. The creature will assume its natural form upon death.

Doppelgängers make excellent use of their natural mimicry to stage ambushes, bait traps, and infiltrate society. Their classic tactic in a dungeon is to take the form of a member of an adventuring party, dispatch him or her, and take his or her place amongst the group until a good time presents itself to kill them or rob them.