It is easy to play, clogs up the board and contributes to your synergy
In the early turns, it can be downright troublesome to have to keep on sacrificing a Pegasus token every upkeep, and there's no worse feeling than plopping down a Sacred MesaSacred Mesa on turn three, paying four mana to feel like you got your money's worth, only to end up sacrificing it all on turn five because you got busy with other problems and now have nothing to show for it
The most insulting part of all is that this effect is not symmetrical, meaning the person playing Drannith Magistrate is completely unaffected by its lockout
Then put the other revealed cards on the bottom of the planar deck in any order
This meant that most midrange and control decks throughout Moderns history have been black-based whether it be Jund, Grixis Control or Deaths Shadow, while many decks have also utilized Thoughtseize in their sideboard as a catch-all card for the different combo decks in the format