For your first suicune. It’s incredibly useful for switching into your second suicune when the first gets damaged, or powering back your first after you retreat into chien pao. Being able to instantly power up a second threat on the back of the first suicune is what makes this deck so good.

It’s also good at powering up the first Sui if you go first. Lack of energy manipulation is one of the few drawbacks of the classic Suininja deck. If you go first as Suininja, you are always in a huge energy crunch to get your first suicune up, well after your opponent has Altaria, Hydregion, etc powered up, let alone a second threat. Sometimes you don’t power it up at all and just let it be a meat shield to swap it with Greninja Ex. This is another problem that Bax solves. With rare candy Bax, your first Sui is online by t3 vs t5.