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
Commons, non-holos, and the gold Burger King promos are usually worth a few dollars
Take a look: Mentor Double strike Preventing combat damage Hexproof Menace Vigilance Treasure token Untap Return card from graveyard Silverquill vs
Dreadhorde Arcanist Dreadhorde Arcanist might not look like much to the average player, but when you consider that older formats are full of incredibly cheap spells, suddenly it comes into focus
That said, it will be particularly important in Theros because playing your removal at the wrong time might lead to your opponent blowing you out via the heroic mechanic
The art felt moodier, with murky backdrops and eerie expressions