If it resolves, you'll follow its instructions and the targeted opponent will mill half of their library
This is really bad, but it also requires you to either hold your most recent card in a second pile or have a judge watch the card you drew
As one might expect, there are a lot of Mice, Rats, and Squirrels in Bloomburrow (although only a single Hamster, and it's confusingly called a gerbil)
The sheer quantity of decks that can take advantage of this trigger is astounding, and we all know that youre going to be flickering exactly one card with this most of the time: Dockside Extortionist
Lightning Bolt was especially important at PT 1, as it was the best clean answer to Black Knight, Order of the Ebon Hand, White Knight, Order of Leitbur, and so on (since both Swords to Plowshares and Terror had giant weaknesses)