Download
Raises the attack stat corresponding to the opponents' weaker defense one stage upon entering battle.
Full effect
When this Pokémon enters battle, its Attack or Special Attack, whichever corresponds to its opponents' weaker total defensive stat, rises one stage. In the event of a tie, Special Attack is raised. This ability also takes effect when acquired during a battle.
In game description
The Pokémon compares an opposing Pokémon's Defense and Sp. Def stats before raising its own Attack or Sp. Atk stat—whichever will be more effective.
Pokemon with Download
Using Download in Cobblemon
Abilities are passive and always active, so Download costs you nothing to run. If it is marked hidden on a species above, expect it to be harder to obtain: servers differ in whether hidden abilities come from breeding, an Ability Patch, or events.
See the Pokedex for which abilities each species can have, and IVs, EVs and breeding for how to actually pass one down.