You may look at the top card of your library at any time.
You may play the top card of your library. If you cast a spell this way, pay life equal to its converted mana cost rather than pay its mana cost.
Tap, Sacrifice ten nonland permanents: Each opponent loses 10 life.
Pros & Cons
- Can't be countered by Flusterstorm.
- Can cast cards using life as a resource instead of mana.
- Artifact for Mox Opal.
- Able to cast spells without a mana cost (See below).
- You are able to take game actions in between (unlike Ad Nauseam).
- Theoretically a win-condition.
- Can use fetchlands & cantrips to "sculpt" top of your library.
- Looking at the top card of your library doesn't randomly provide death (unlike Ad Nauseam).
- Ability can span over multiple turns, easier to "go-off" multiple times.
- You can cast cards from your hand (unlike Experimental Frenzy).
Something people may not realize is like Mind's Desire, you're able to cast spells without a converted mana cost off of Bolas's Citadel.
117.6a If an unpayable cost is increased by an effect or an additional cost is imposed, the cost is still unpayable. If an alternative cost is applied to an unpayable cost, including an effect that allows a player to cast a spell without paying its mana cost, the alternative cost may be paid.
This is very exciting, especially with cards like Ancestral Vision or Lotus Bloom. But I think it's important to not get caught up in, "the danger of cool things". In general, you don't want cards that don't do anything before you "combo-off" especially ones that don't do anything until turns four or five. It's part of the reason our deck struggles sometimes with Mox Opal as it's only sometimes functional before your Ad Nauseam, but at the very worst adds free storm. Cards like Lotus Bloom and Ancestral Visions can't even do that!
In theory, you could load your deck up with Ancestral Visions and Lotus Bloom, use Brainstorm and Ponders to sculpt them to the proper places in your library similar to the Miracle mechanic. The issue with this is those things take time and time plays into the control deck's strategy where it's the opposite of what you'd like to do for combo. Which is why strategies like High Tide or Doomsday have fallen to the sidelines. Turns two to three are the fundamental turn for most combo decks and cards like Lotus Bloom or Ancestral Visions don't play into that. While you may blow your opponents out with these cards, are they really improving your odds?
Post-Bolas's Citadel you'll be able to cast almost every single spell in your deck using your life total as a resource. If you're not, the deck has cards like Mox Opal, Chrome Mox, Lotus Petal, Lion's Eye Diamond, Rite of Flame, and Dark Ritual. Does it really need Lotus Bloom? Not likely. Similar things could be said of Ancestral Visions with Ponder, Brainstorm, and even Preordain.
In Vintage, Paradoxical Outcome storm will certainly add in Bolas's Citadel as a target for Tinker. It's essentially a "tutorable" Yawgmoth's Bargain that you're able to cheat into play in a format where the power-level of the cards is much higher. I personally can't wait to try this out.
Is it playable?
Time will tell, it certainly needs to be tested. My initial gut reaction is that it's likely worse than Ad Nauseam, but it's powerful enough where I think it deserves to be tested and built around.
Which brings me to my next point, due to multiple lands in a row being bad, I believe any Bolas's Citadel storm decks need to be constructed in a way to abuse cards like Mox Opal or other free accelerants — possibly even Land Grant. You need to reduce your probability of fizzling, while not making your deck worse.
While Ad Nauseam's cost-restriction is your life total, Bolas's Citadel's are both lands and your life-total which might be the tipping point.
These are all speculations and I could be wrong, but these are my initial reactions. Thanks for reading and keep storming!