(So far, the only one of those cards to return to the Core Set was Llanowar Elves, in the Ninth Edition.) The Circle of Protection series, a perennial core set entity, was modified from common to uncommon status
Displacer Kitten is the most important card, of course, a premier blink engine that's not had enough printings, given how many decks it's great in
Alternatively, if you haven't submitted a decklist yet, you will see a reminder on the public tournament page that will take you to the submission form
With the previous set being Bloomburrow, it also has Shadowmore vibes as Shadowmore followed Lorwyn after the Great Aurora set in a haunted house
Wizards knew that they needed a simpler way to template cards with these abilities, and preferably one they could print at low mana costs without accidentally breaking every permanent with triggered abilities