Effect Spore

Has a 30% chance of inflcting either paralysis, poison, or sleep on attacking Pokémon on contact.

Full effect

Whenever a move makes contact with this Pokémon, the move's user has a 30% chance of being paralyzed, poisoned, or put to sleep, chosen at random. Nothing is done to compensate if the move's user is immune to one of these ailments; there is simply a lower chance that the move's user will be affected.

In game description

Contact with the Pokémon may inflict poison, sleep, or paralysis on the attacker.

Pokemon with Effect Spore

#0045

Vileplume hidden #0046

Paras #0047

Parasect #0285

Shroomish #0286

Breloom #0590

Foongus #0591

Amoonguss #0755

Morelull #0756

Shiinotic #0829

Gossifleur hidden #0830

Eldegoss hidden

Using Effect Spore in Cobblemon

Abilities are passive and always active, so Effect Spore 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.