This isnt an enters-the-battlefield effect, though
Designed especially for new players, Gateway includes everything you and a friend need to start playing immediately
From iconic creatures like Eternal Witness to the meanest of monsters like Atraxa, Grand Unifier, enter triggers are a way of guaranteeing a permanent comes with some value no matter how quickly its removed afterwards
Sagas like The Mending of Dominaria and The Eldest Reborn help you put creatures and lands into play
Giving your team +2/+2 often buffs creatures enough to attack profitably, and its easy to spew artifacts across the board so the trigger deals lots of damage (which you can multiply with Furnace of Rath and Dictate of the Twin Gods), making Sentinel Sarah Lyons look like a powerful aggressive commander
Kitt is a four-drop 3/3 so a bit behind the curve in size for those colors, but has two abilities