You can find these Buy-a-box promos at certain local game stores
(2025-09-19) If you cast a spell for another cost "rather than pay its mana cost," you can't choose to cast it for any alternative costs
But this only works for cards found in main sets and to a lesser extent special sets since they're usually kept in production for a while (and if what TPCi said in the past is true, will continue to be printed as long as there's demand for 'em and they're not rotated out), this rule doesn't work for promos since they're usually only given away during a certain window of time and given a limited print run that's long enough to fit the predicted demand
They are the top competition for their respective slots
Prismatic had the right idea where it banned fast mana like Mana Crypt and Sol Ring, tutors (ranging from Mystical Teachings to Demonic Tutor), and then any other degenerate cards like Memory Jar, Necropotence, Yawgmoth's Will, or Gush
Jenson Carthalion, Druid Exile Jenson Carthalion, Druid Exile rewards you for casting multicolored spells by letting you scry 1, and if that spell is all colors, you get a free 4/4 Angel with flying and vigilance
