In Star Wars: Rebels (“Rise of the Old Masters”), Kanan and Ezra go in search of Jedi Master Luminara Unduli, whom they believe to have survived and to be in Imperial custody. They discover what they believe to be her, but is actually a hologram.
It is revealed to be a trap by the Grand Inquisitor:
INQUISITOR: Yes, I’m afraid Master Luminara died with the Republic. But her bones continue to serve the Empire, luring the last Jedi to their ends.
Star Wars: Rebels, “Rise of the Old Masters”
What purpose did Unduli’s remains serve? The trap apparently consisted of false messages and a hologram, and the hologram was arguably not even necessary, only serving to get Kanan and Ezra into a certain room.
Why did the Empire need her body? Why did they use it as part of the trap?