Is there a shapeshifter that needs to keep its quarry alive?

Question

My question is regarding the rules of shapeshifters of all kinds in D&D 4e. I'm designing a plot in which I want to have a Changeling (or something like it) replace a prominent member of society, with the idea that the party will eventually save the man and expose the shapeshifter. My friend pointed out that Changelings do not necessarily need to keep their quarry alive in order to maintain the illusion of being that person.

My question is: In 4e, is there a shapeshifting race that NEEDS to keep someone alive in order to maintain the shapeshift? I know it is easily house ruled, but if something like this is already in the rules and I haven't found it, I would like to know. I try to keep house rules to a minimum in my campaigns.

Answer 1

According to (the archived version of) a 2013 article from the Wizards' website:

In addition to their shapechanging, doppelgangers have the ability to read thoughts. In the short term, a doppelganger can read thoughts to aid it when tricking people around it. When impersonating a specific victim, a doppelganger likes to spend an hour or so every day plundering its victim's mind for memories it can use to make its disguise more convincing. Thus, a doppelganger that is serious about maintaining a specific false identity usually keeps its victims alive and close at hand so it can behave and speak authentically. (This characteristic facilitates an adventure where player characters can rescue someone who has been replaced by a doppelganger.)

There are additionally many possible story reasons for keeping the target alive.

• Information

  It may be important to keep the target alive to get more information from him, just looking, speaking, and behaving like your target is not always enough.

• Leverage

  If the changeling gets caught, he might want the target for a bargaining chip.

• Proof

  The changeling might require samples or evidence of the targets body (hair, blood, a finger?) to prove his identity in certain situations

• Disguise

  The changelings ability might require continuous samples of the target to keep working. (Or maybe the changeling can only morph into a target he touches or sees)

These are just some reasons, and each of those reasons can be easily expanded, played with, or combined for your story.

Answer 2

Any shapeshifter might need to do that. Successfully impersonating someone has two main parts: looking (sounding, smelling, whatever) like the target, and having the same knowledge.

If you want to appear as the Earl's long lost son, fooling even your wetnurse and your tutor, you have to know about intimate events shared with them. After grilling your captive for details, something might still come up in conversations with "old acquaintances" that you forgot to ask about. So if you keep him alive in a nearby location, you can always torture him for more answers.

Watch the White Collar season 5 episode 5, it has mostly the same plot.