If neither of those apply to you, this wont appeal to you, and the same goes for any of the other
Putting in the effort to clone or flicker Sin could provide an overwhelming force of value
If another player gains control of Lightning, you won't be able to play any of the exiled cards, even if you later regain control of Lightning
It boasts a host of taxation (Ghostly Prison), prevention (Blazing Archon), and protection (Teferi's Protection) effects that make attacking you difficult, if not impossible
The Maze doesn't take any mana to use, nor is in a color identity, but the Haven taps for mana so I consider them roughly equal
His activated ability exiles and casts cards off the top of your library for free