What it doesn't have is on-demand, instant-speed answers
Some top black commanders include Anowon, focusing on vampire synergies, and Chainer, excelling in creature recursion
Whenever a land enters the battlefield under your control, you can have target player mill three cards
Vise is a powerful punisher card but it typically punishes things you are decent against and not things you struggle with
It's difficult to kill in combat with an 8/8 body, it pushes serious damage with trample, and most of all, it has hexproof to ignore removal spells and abilities of all kinds
While two mana for two cards each turn is definitely a good rate, there is a very real delay with Sylvan Library: it takes a whole turn cycle to actually do anything, which, as well see with the rest of the list, makes it fairly slow by comparison