Deck name comes from Flux Pavilion's dubstep track "Bass Cannon", and in this case refers to the combo of Bolas's Citadel and Aetherflux Reservoir's life snipe ability.

Gameplan:
The only attacker is Atraxa, Praetors' Voice. All other creatures are there for utility or blocking planeswalkers. The deck focuses on pillowfort / defense, control, counterspell, ramp, and card draw. The basic idea is to turtle and appear non-threatening, politicking (agreeing not to attack people with Atraxa, proliferating other player's counters, etc.) while mana ramping for game-ending big sorceries. Most of the planeswalkers have passive effects, or provide creature destruction/exile. They also distract players from my artifacts and provide creature token blockers. The deck has numerous cards to retrieve artifacts from the graveyard to keep the Aetherflux Reservoir + Bolas's Citadel combo from being broken, or to recover Astral Cornucopia (typically my biggest mana source by far). Can even recover artifacts from exile with Karn, the Great Creator. Most of the planeswalkers have card draw or Scry abilities, and in addition Soothsaying all assist with moving lands off of the library top or discarding good spells ONTO the library for Bolas's Citadel to keep working. Ichormoon Gauntlet, Tekuthal, Inexorable Tide, Flux Channeler = high probability I'll be proliferating multiple times per turn. Blink shenanigans for Ezuri, Stalker of Spheres or Deepglow Skate also provide explosive growth.

Ramp (11)

Astral Cornucopia, Chromatic Lantern, Everflowing Chalice, Mana Vault, Pentad Prism, Sol Ring
Wrenn and Realmbreaker: mana filter
Sword of Feast and Famine untaps all lands
Tezzeret, Master of the Bridge makes creatures and planeswalkers cheaper
Tezzeret the Seeker and Teferi, Temporal Archmage can untap mana rocks

Card Draw & Card Advantage (15)

Mystic Remora, Rhystic Study, Teferi, Time Raveler, Liliana, Dreadhorde General, Erebos, God of the Dead for card draw
Demonic Tutor, Vampiric Tutor, Liliana Vess, Tezzeret the Seeker for tutoring
Diabolic Vision, Narset Parter of Veils, Teferi, Temporal Archmage for scrying/draw
Aminatou, the Fateshifter, Brainstorm for card draw and also topdeck manipulation
Kasmina, Enigma Sage scrys and gives every PW the ability to move lands off the top of my library

Removal (10)

Cyclonic Rift, Urza's Ruinous Blast, Elspeth, Sun's Champion boardwipes
Ashiok, Nightmare Muse to bounce + exile
Despark, Kaya, Bane of the Dead, Dakkon, Shadow Slayer, and The Wanderer targeted creature exile
Teferi, Time Raveler targeted artifact/creature/enchantment bounce
Liliana, Dreadhorde General player sacs two creatures, or ults to sac almost their whole board

Token Producers (5)

Ashiok, Nightmare Muse, Elspeth, Sun's Champion, Liliana, Dreadhorde General, Kasmina, Enigma Sage, Field of the Dead

Finishers (9)

Aetherflux Reservoir: 50-life snipe
Bolas's Citadel: activated ability sac'ing tokens or other permanents in an emergency
Exsanguinate, Torment of Hailfire, Debt to the Deathless: all big X sorceries
Eerie Ultimatum after a boardwipe
Liliana Vess ults with full graveyards to steal a ton of creatures
Liliana, Dreadhorde General ults
Atraxa equipped with both Sword of Feast and Famine and Sword of Truth and Justice beats people in the face for commander damage. The proliferating +1/+1 counter quickly turns into lethal commander damage if she connects twice per player.

Eternity Vessel: restores life lost from Bolas's Citadel, especially after hitting a topdeck land. Benefits from proliferation and/or blinking
The Chain Veil: even more planeswalker activations

High-Priority Planned Changes:
Norn's Choirmaster for more proliferate triggers, including the option of blinking Atraxa
Tainted Sigil: lifegain artifact synergy with Bolas's Citadel, Aetherflux Reservoir
Kaya the Inexorable: cast cards from exile, more targeted removal
Ob Nixilis of the Black Oath: creates a strong flying blocker, has lifegain and ults for lifegain sac outlet

Myojin of Cryptic Dreams: possibly a "win more" card due to high CMC and slow effectiveness. Use to copy Aetherflux Reservoir, Inexorable Tide, etc...
Empowered Autogenerator + Filigree Sages: mana ramp