Okay, so Im Battling A Piplup, and it uses Substitute. Then it uses Toxic on :
1-My Magic Bounce Espeon
2-My Synchronize Umbreon
Im wondering what happens because the Piplup is Behind a sub.
Magic Bounce will bounce back Toxic, but it will fail to affect your Pokemon because it's behind a substitute.
When you use Toxic, Synchronise affects you even if you're behind a substitute.
Source: Experience.