While the -2/-2 applies only to creatures that are on the battlefield as Malicious Eclipse resolves, the replacement effect applies to all creatures opponents control that turn, including ones that enter the battlefield after Malicious Eclipse resolves, noncreatures that become creatures after Malicious Eclipse resolves, and creatures that become controlled by opponents after Malicious Eclipse resolves
Courtesy of Wizards of the Coast (WotC) and Ryuzo Fujie, take a look at this unique enchantment from Modern Horizons 2 Out of Time
The first effect can play into the exhaust effect, being able to take someone out in the late stages of the game
Rosie Cotton of South Lane Yeah, so Id be remiss if I didnt mention an uncommon that happens to combo with another uncommon (Scurry Oak) to make infinite creatures alongside an absurdly large treefolk
While its solitary, its not alone, and it knows