Swarm
Strengthens Bug moves to inflict 1.5× damage at 1/3 max HP or less.
Full effect
When this Pokémon has 1/3 or less of its HP remaining, its Bug-type moves inflict 1.5× as much regular damage. Overworld: If the lead Pokémon has this ability, the wild encounter rate is increased.
In game description
Powers up Bug-type moves when the Pokémon's HP is low.
Pokemon with Swarm
#0015
Beedrill
#0123
Scyther
#0165
Ledyba
#0166
Ledian
#0167
Spinarak
#0168
Ariados
#0212
Scizor
#0214
Heracross
#0267
Beautifly
#0313
Volbeat
#0402
Kricketune
#0414
Mothim
#0540
Sewaddle
#0542
Leavanny
#0543
Venipede
#0544
Whirlipede
#0545
Scolipede
#0588
Karrablast
#0589
Escavalier
#0595
Joltik
hidden
#0596
Galvantula
hidden
#0632
Durant
#0636
Larvesta
hidden
#0637
Volcarona
hidden
#0736
Grubbin
#0824
Blipbug
#0825
Dottler
#0826
Orbeetle
#0900
Kleavor
#0919
Nymble
#0920
Lokix
Beedrill
#0123
Scyther
#0165
Ledyba
#0166
Ledian
#0167
Spinarak
#0168
Ariados
#0212
Scizor
#0214
Heracross
#0267
Beautifly
#0313
Volbeat
#0402
Kricketune
#0414
Mothim
#0540
Sewaddle
#0542
Leavanny
#0543
Venipede
#0544
Whirlipede
#0545
Scolipede
#0588
Karrablast
#0589
Escavalier
#0595
Joltik
hidden
#0596
Galvantula
hidden
#0632
Durant
#0636
Larvesta
hidden
#0637
Volcarona
hidden
#0736
Grubbin
#0824
Blipbug
#0825
Dottler
#0826
Orbeetle
#0900
Kleavor
#0919
Nymble
#0920
Lokix
Using Swarm in Cobblemon
Abilities are passive and always active, so Swarm 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.