While its not a powerful creature, thats by design
This deck turns quiet lifegain into an unstoppable storm of buffs, board control, and massive game-ending swings
But the gist of things is that in the plane of Dominaria, two powerful Planeswalker brothers called Urza and Mishra (who were name-dropped all the way back in the base set) waged a war with the powerful magical artifacts they found in a conflict called the Brothers' War, lasting for years
Those decks often set up for many turns by simply ramping more lands into play, and Iridescent Vinelasher is both an alternate win-con and an easy way to set up the magic number of 18 life that Valakut needs to combo kill a player in Modern
If you are playing against a deck with Wasteland, crack the Bloodstained Mire to find a basic Swamp (otherwise play Badlands), then cast Entomb
Given Krrik is popular on its own, Defiler of Flesh will at the very least find a home in Krrik decks