This is chaotic, as you can get practically any spell from your deck, be it one of the biggest, baddest of the Eldrazi titans or a Llanowar Elves
For example, you may still want to bring a Standard deck to play for fun between rounds, a trade binder, pen and paper to keep track of life, and even a water bottle
The card exiles two permanents when it hits the board, and the defending player exiles twenty more cards whenever Ulamog attacks.
There are only a handful of Commander decks where card draw is a key mechanic rather than simply an advantage and a way to get slightly ahead
Beyond just being rare, thanks in part to the limited-run printing of Secret Lair drops, and their Bonus Cards, Mana Vault is insanely strong
There are so many ways to try to combo off with Bolas's Citadel, whether thats various kinds of storm decks in Modern, Jund Citadel in Pioneer, or that deck youve seen in Historic with Bartered Cow and Refurbish