Of course, the Reanimator player casting this on turn one or two will frequently be bringing back Grave Titan or Archon of Cruelty, while the other player may not even have a creature in their graveyard yet to choose making this one of the very best early game reanimation spells ever
Steelbane Hydra Steelbane Hydra is a solid green creature for artifact hate that can be built around to great effect
Ralts itself is not particularly powerful, but once it reaches its final Evolution, it can either become a powerful Fairy known as Gardevoir, or a Fighting-type known as Gallade
Some of the monsters you'll be able to collect are Greninja, Lapras, Drifloon, Zorua, Ho-Oh, Xerneas, Kyogre, Lunala, Zekrom, Zacian, Slowpoke (in a well!), Unown, and Meowth, among others
That would give you the upper hand against monsters with high attack or defense