And this Xatu's function as a counter to the Shell Smash + Baton Pass strategy is also incredibly simple to understand. Since Xatu is immune to Spore, it can easily switch into Smeargle without fear of anything. If Smeargle Spores Xatu on the switch, then it puts itself to sleep, which is excellent. If it Shell Smashes on the switch, Xatu just uses Haze on the turn Smeargle Baton Passes its stat boosts to another Pokémon, nullifying those boosts on that turn and therefore effectively countering the Shell Smash + Baton Pass strategy. This is notable because it is the one and only 100% SmashPass counter in existence - even Yawn Espeon is not a guaranteed counter, as Smeargle could use Shell Smash as Espeon switches in, and then use Substitute on the following turn when Espeon uses Yawn. And while Imposter Ditto is famed as the one responsible for the death of SmashPass in DW Ubers, it is by definition not a counter, but rather a revenge-killer.