Cabal Ritual and Dark Ritual Speaking of efficient mana acceleration, you dont get much better than the rates offered by Cabal Ritual and Dark Ritual
What is
Both properties have very similar lore, even if the specifics of each have unique and interesting spins on everything
Plus, because Toski can't ever be countered, even those pesky Mono-Blue players will be forced to sit there and let this little card-generating machine resolve
Prepare Expending Blockers If you have prepared, non-deploying expend champion(s) (Dark Assassin, Dark Leader, Murderous Necromancer, Necromancer Lord, Succubus, High King, White Knight, Djinn of the Sands, Forcemage Apprentice, Keeper of Secrets, Time Bender, Hunting Raptors, Pack Alpha, Elara The Lycomancer, Helion the Dominator, and/or Rabble Rouser), Feint can let you trigger them twice in one turn
Niche would be an understatement but still not a card that is unplayable in cube