@TheJaylor You’re correct. I found this under the Unique entry in the REG:
Players may only control one of each unique card in their territory, set-aside area, or their side of battle.
The 50 card type 1 deck building rule regarding unique characters, however, still remains as he could not have the same unique prophet in his deck building. The scenario he presented would realistically only be able to be done in a Type 2 deck, unless he rescued the unique prophet then took permanent control of an opponent’s same hero.