You can usually mulligan to six to try and find a Flourishing Fox, since games where you have that critter on turn one can be very lopsided
If X is greater than the number of cards in the targeted player's library, you can't choose to have them mill any cards
Even the much cheaper English variations of the Traveling Chocobo can range anywhere between $700 all the way up to $900, with no signs of slowing down, easily surpassing any other card in the set by a landslide
If you're especially daring, you could try Helm of the Gods, Demonic Pact, Tainted Remedy or Starfield of Nyx
Faller's Faithful Ever since ETB stuff arrived Nekrataals have been loved, but they cost four and then are two Black to shut down interaction like Ravenous Chupacabra, this just costs three splashable and it is 3/1 size