You choose an opponent while Sandstone Oracle's ability is resolving. No player may take actions between the time you make this choice and the time you draw cards.
10-11-2020
wotc
To draw cards equal to the difference, first determine how many cards you'll draw, then draw that many cards, as modified by replacement effects. For example, if you have two cards in hand and the chosen opponent has five, Thought Reflection will cause you to draw six cards instead of three.
Random a card of Magic: The Gathering (MTG), but you can also roll the D20 dice, random a Planeswalker, have fun with the random rules and more.