Impulse (T1, Ext, S, Block) Casting Impulse feels like cheating
I narrowed down my list quite a bit, to the point where I left off perfectly viable cards that Im sure plenty of players have had success with
Right now, according to TCGplayer, there are four gold-stamped art cards with a market price above $10: Y'shtola, Night's Blessed (Art card #53) $16.05 Nibelheim Aflame (Art card #35) $14.02 Sephiroth, Fabled SOLDIER (Art card #44) $10.47 Tifa, Martial Artist (Art card #52) $10.31 (this uses a stamped planeswalker symbol instead of an artist signature) Beyond those, there are another eight art cards currently above $5 (all of which contain the gold-stamped artist signature)
The thing to remember about Sepharas alternate cost is that it only pays the spells mana cost
A Note on Card Randomization for Booster Pack Packaging The main producers of booster packs games like Pokmon, Magic the Gathering, or Yu-Gi-Oh