Fauna Shaman Elf decks often have a plethora of different creatures they want on the battlefield simultaneously, and sometimes its hard to get the exact creature you need at the right time
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
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
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
Of the Enchanted Rares, the Elsa card really stands out
In particular if you are more concerned with picking off specific targets from Meren of Clan Nel TothMeren of Clan Nel Toth's yard or other graveyard strategies in your friendly neighborhood Commander playgroup