When they first joined, Anders would sometimes think of Justice as his imaginary friend.
"You know," Anders explained to Varric once, "that voice in your head that isn't exactly you, but isn't exactly not you? So you give it a name, and there you go, an imaginary friend."
Over time, Justice began to understand. There was a voice in their head that wasn't exactly Anders, that wasn't exactly Justice, but had not been created from whole cloth.
Its voice grew louder, and they both heard its strident calls to action.
Together they named their imaginary friend.
They called him Vengeance.