If they cant (or if you use the mana from the Cornucopia to cast something cheap and disrupt their attempt) then theres every chance the mana ramp leads to an early board wipe after which the continued lifegain can bury their hopes even if the Cornucopia player lacks a real haymaker to follow up
However, only one set managed to do both, as "Twilight Masquerade" was a great set for the game
Portent was amazing in Standard, albeit frequently misunderstood
It's only three mana for such a powerful effect, but it does have its drawbacks to balance out that power
If youre playing with Oracle, this is a good backup, however, and its iconic for a reason
While they are seeing some testing, its unclear if Bloodthirsty Conqueror will become a competitive staple going forward