Aurelia's Fury saw a tiny bit of play but was just too clunky to be useful in the way you want a spell like that to be
To give you an idea of how good blue instants are compared to other colors, blue would have over 50% of a "Top 50 Instants of All Time" list (and take six of the top ten slots)
Because paying X is part of the normal casting cost, paying an alternative cost for these cards will result in X=0 unless the alternative cost itself specifies a value for X, such as Lantern Flare or Disrupting Shoal
You can check out pokemonsim.com right here For the most part Ive broken it down by slot within the pack and rarity within the slot
However, the card that truly resembles the latter is Ugin's Labyrinth, as it allows you to play a turn 1 Mind Stone for a potential turn 2 4-drop
Explore was a very popular mechanic in the original Ixalan block and naturally, it returned in The Lost Caverns of Ixalan and Lost Caverns of Ixalan Commander