The timing will be specified in the card, or it will be implicit because of the card type
For example, Everlasting Torment can make Circle of Protection: Black sit there uselessly in play, while Spirit of the Labyrinth effectively blanks a number of "draw a lot of cards" decks
Armageddon Armageddon is the OG mass land destruction, followed by Ravages of War
The Izzet dragon is one of the better Izzet commanders out there, who loves spellslinger decks that draw tons of cards
With Xyris leading the charge, every draw turns into overwhelming value, swarming your opponents with creatures while keeping your hand full of answers and threats
Lorcana's lore will also grow with Into the Inklands, as narrative can be learned through the quotes and descriptive text on the cards