Not a lot needs to be said about Lightning Bolt and the weight it has carried throughout the games history
It stops spells you play from being countered, it gives permanents you control Hexproof from both Blue and Black cards, and it lets you draw a card if an opponent has played a Blue or Black card
Ursulas Return is an important set for the Disney Lorcana game, further establishing it as a mature game with deep strategy
Everything else can be found in Draft and Set Boosters, though at a lower frequency
The archetypes which want those kinds of cards are red-white, green-white, black-red, and (to some degree) green red
Almost every bomb in limited is a creature, and this color combination gives you the most tools to answer them, as well as discard for other bombs