Cavern of Souls As Commander grew in popularity, so did players' desire for this powerful land
One of the signs that sweep wasn't a very deep mechanic was that we only printed four of them (one of many reasons I believe using an ability word for sweep was a mistake)
This allows us to make cards that showcase things that happened off-camera in a sense, which we can show on different kinds of cards (for example, artifacts, enchantments, or land) rather than something like a creature card
We just saw Ob Nixilis, Captive Kingpin get printed in Mach of the Machine: The Aftermath and it turns out that in the end, the card did not work with Rakdos Charm the way we wanted it to
While color pairs have previously been well served with cards like Bonny Pall, Clearcutter, its now time for mono-colored cards to receive a power boost