The notion of altering one’s face may be ideal from a gameplay perspective, but from a lore standpoint it’s crazier than a barrel full of Orcs. The ability to take on the faces of loved ones, confidants and infiltrate places in plain sight makes it a game-breaking tool for any assassin or thief. As such, in most universes, shape-shifting is a power reserved for the most dangerous of villains. It’s a rare practice, a difficult feat, a taboo. It is not offered to random strangers for the cost of an ebony mace. After all, if such skills were available to everyone, it would destroy the very concept of physical identity. If anyone can be anyone, then there’s no guarantee that anyone is anyone.
Your spouse could be your neighbor, looking for a taste. Your child may be some orphan who wanted a better life. The guardsman who teases you about your stolen sweetroll could be the thief who stole it. Hell, he could be Ulfric Stormcloak. He’d certainly have the face for it. All it takes is some gold and a smith willing to forge it.
The elven sword Pelgurt asks you to retrieve is just that. A forgery. It’s a stranger posing as a member of the family. It wears its face, it bears its markings, but it has none of the history. Nevertheless, its resemblance alone is enough for Vartheim to question whether the sword he’s stolen is real. The same is true for the face of the mercenary Benild. At no point does he consider that her identity is as false as Pelgurt’s sword.
In the end, the story of The Elven Sword is one about deception. Whether it’s the make of a sword or the face on a skull, when identities can be bought and bartered for, it’s best not to trust anyone.