This means that abilities that trigger whenever a creature attacks won't trigger when it enters the battlefield attacking
Exile this creature at the beginning of the next end step, then you may cast it from exile on a later turn.) Even across the Edge, a dog is still a dog
However, unlike Pokmon V and the earlier Pokmon EX (capital EX) from previous sets, these are more akin to the old Pokmon-ex from the 3rd Generation, in the sense that evolved Pokmon ex exist
You'll be able to cast cards you exile if timing rules allow (so, instants, mostly), but you won't be able to play a land that turn
But Mega Greninja ex is just one of the new Mega Evolution Pokmon ex that can be found in this expansion
Whats more important, the most problematic enchantment played (Leyline of the Void) prevents us from flashing it back