Every ability

Shadow Tag

Prevents foes from choosing to switch unless they also have this Ability.

Standard ability
2
Pokémon
Hidden ability
3
Pokémon
Only in battle
1
Pokémon

In detail

Prevents opposing Pokémon from choosing to switch out, unless they are holding a Shed Shell, are a Ghost type, or also have this Ability.

Pokémon that can have it

6

Standard ability2Any one caught or hatched may have it

Hidden ability3Only one with its hidden ability has it

Only in battle1A forme it takes mid-battle, like a Mega Evolution