This doesnt get around Commander Tax, unfortunately, but does reduce Sepharas cost by a lot
Collective Brutality does a lot of things for a black Standard deck
this late junk era, but there are some important cards from this time
it is not required that there be an empty space in the spot where the location is placed or moves to
The most likely reasons are if it's sacrificed, if it's legendary and another legendary permanent with the same name is controlled by the same player, if it's a planeswalker and another planeswalker with the same subtype is controlled by the same player, if it's a creature with toughness 0 or less, or if it's an Aura that's either unattached or attached to something illegal
However, these services also have their issues