Any opponent who wants to challenge this character will have to discard their full hand to do so, making it hard to stop her effective lore generation without a Banish card or a major sacrifice
There are a few ways around it, with cards like Teferis Protection, but those cards are few and far between
Here are some incentives for it: Cards like Corrupt, Cabal Coffers, Mutilate, and Defile want you to play as many swamps as possible, so their efficiency is maximized in mono-black decks
In addition, Void Winnower shuts down blockers with even mana costs, which makes it easier for huge threats like the 11/9 Void Winnower to attack
The card was so powerful that it warped the entire metagame around itself, forcing players to run specific hate cards in their main decks just to have a chance