The landscape of Legacy is very different in the wake of the banning of Sensei's Divining Top. There’s now space for multiple styles of control deck, ranging from Portent plus Terminus to various flavors of Stoneforge Mystic or Monastery Mentor. When there’s that much variation among control strategies in Legacy, the question becomes this: how do you effectively pressure their planeswalkers and ensure that you can stay ahead on resources? This build by Midnight_s2000 may be a great solution:

Blue-Black Control - Legacy | Midnight_s2000, 5-0 Legacy League

• Creatures (7)
• 3 Snapcaster Mage
• 4 True-Name Nemesis

• Planeswalkers (3)
• 3 Jace, the Mind Sculptor

• Instants (17)
• 1 Counterspell
• 2 Diabolic Edict
• 3 Force of Will
• 3 Spell Pierce
• 4 Brainstorm
• 4 Fatal Push

• Sorceries (9)
• 2 Ponder
• 3 Thoughtseize
• 4 Hymn to Tourach

• Artifacts (1)
• 1 Umezawa's Jitte

• Lands (23)
• 2 Swamp
• 5 Island
• 1 Marsh Flats
• 3 Cavern of Souls
• 4 Flooded Strand
• 4 Polluted Delta
• 4 Underground Sea

• Sideboard (15)
• 2 Back to Basics
• 2 Flusterstorm
• 1 Liliana, the Last Hope
• 1 Marsh Casualtie
• 1 Pithing Needle
• 2 Ratchet Bomb
• 2 Relic of Progenitus
• 1 Surgical Extraction
• 3 Vendilion Clique

Buy This Deck

The answer is Cavern of Souls plus True-Name Nemesis. It turns out that when you’re only playing two colors, you can afford space for Cavern of Souls, which generate an enormous amount of value by ensuring that your Snapcaster Mages and True-Name Nemesises resolve, which puts you in a great spot when backed up by counterspells and discard.

The format as a whole isn’t set up especially well to fight against True-Name Nemesis right now. Terminus has been a format-defining sweeper for such a long time that the metagame hasn’t adjusted to its new decreased presence. That puts True-Name Nemesis in a great place to dominate boards, murder planeswalkers, and get your opponents dead.

If you’re looking for a way to gain an edge in Blue mirrors, this might be exactly what you’re looking for. You’re likely to have a reasonable edge purely on gameplan in the first game, and have plenty of space for game-ending sideboard cards like Back to Basics and Dread of Night depending on what exactly it is your opponent is trying to do.