It's likely The One Ring will be most powerful in MTG 's Standard and Commander formats, although it may prove to be too slow for Modern, Legacy and Vintage
Might (76) Duel Decks: Nissa vs
This card's Union Gain attaches two Water energy cards to Greninja, and this'll help with pretty much every attack it has - whether that's dealing 130 direct damage with Aqua Edge, hitting every opposing Benched Pokmon for 100 damage with Twister Shuriken, or stopping a defending Pokmon from retreating with Waterfall Bind (oh, and dealing 180 damage)
The strength/weakness system, although unexplained and surprising, is pretty cool once you get used to it
Plus, Sword of the Animist also gives a helpful power boost to Karlach which gives her second attack a little more oomph
Instant-speed, near-free sacrifice outlets are always worth considering