Skullclamp Most of the best cards in this ranking cost between $20-40, but you can get Skullclamp for a fraction of that, thanks to its many recent reprints
Once it resolves, it will remain in effect until the game ends, Ride the Shoopuf's leaves the battlefield, or some subsequent effect changes its characteristics, whichever comes first
In Modern, building with Concealing Curtains gets a bit trickier, but if you want to avoid the Rakdos trap of losing to Sanctifier en-Vec, I can see Concealing Curtains as a one-drop of choice for an Esper or Sultai Lurrus deck
Much of blacks ramp is ritual-based, or cards that produce a burst of mana for a single turn
Seventeen Ally decks were even desperate enough to turn to Yarok, the DesecratedYarok, the Desecrated at the helm, which shows how hard-up Ally decks were for PanharmoniconPanharmonicon effects