Looking back now, 5 mana is an awful lot to ask of an enchantment that doesnt do anything when it enters the battlefield, but if allowed to sit on the battlefield after a board wipe or a couple turns of play from an Aristocrats strategy (decks that derive value from sacrificing creatures), Black Market can quickly generate game-winning amounts of black mana
Professor Dellian Fels emblem gets around that
#1: Yawgmoths Will Yawgmoths Will can be easy for non-Vintage players to underestimate since so many lists seem to feature just two Yawgmoths Wills, even when people could have played four
On the other hand, a fair Gifts Ungiven is very fun and akin to Fact or Fiction in the politics and interplay between players it can create
It may be tempting to stack everything onto your commander and start swinging, but that can make Killian a huge target very quickly
Even if you are ahead in ever metric, a 4/5 is a perfectly acceptable body to widen your lead