it lets you play both black Werewolves, as well as white effects like Rule of Law and Deafening Silence
You need to be heavy on creatures, both to turn this into card advantage rather than card filtration and to harmonize it profitably, but thats an extremely low ask for this much power
It's obviously a hyper-specific hoser against a narrow set of decks, and Slivers that grant abilities across the entire battlefield are a ten on Mark Rosewater's "Storm Scale." That means symmetrical Sliver abilities aren't even a consideration anymore.
Replacement effects are unaffected by Fractured Realm's ability
Brawl Legal Vintage Legal Timeless Legal Commander Legal Pauper Not Legal Oathbreaker Legal Penny Legal Toolbox Notes and Rules Information for Naru Meha, Master Wizard: Because damage remains marked on a creature until it's removed as the turn ends, nonlethal damage dealt to a Wizard you control may become lethal if Naru leaves the battlefield during that turn
(Mentioned in the layer files also)