Randomizer? Where in the game?

[Erina]

* New Randomizer Mode: In it, your starter and all wild and trainer encounters will be replaced by completely random Pokémon, for a wacky and challenging game-changing experience. Unlocked after completing the game at least once. (Load a completed save once to register this achievement)

The box to enable Randomizer can be found under the Custom Settings when starting a New Game.

Ah.  Thanks!  Seems like I've got to get through the whole experience then...  Guess it makes sense though.  Get used to the game, see what it has to offer, beat it to get used to it, THEN go for the crazy mode.  I wonder if you can do Randomizer AND the Nuzloke (Forgot how to spell it, sorry) modes at once...  If you can, that'll make for an insane challenge.  Only catch one Pokemon per route, AND they're random.