The Pokémon has a little of its HP restored when withdrawn from battle.
Effect
This Pokémon regains 1/3 of its maximum HP when it is switched out for another Pokémon under any circumstances other than having fainted. This ability does not take effect when a battle ends.
Pokémon with this ability (27)
#079
Slowpoke
#080
Slowbro
#114
Tangela
#199
Slowking
#222
Corsola
#250
Ho Oh
#465
Tangrowth
#531
Audino
#577
Solosis
#578
Duosion
#579
Reuniclus
#590
Foongus
#591
Amoonguss
#594
Alomomola
#619
Mienfoo
#620
Mienshao
#747
Mareanie
#748
Toxapex
#829
Gossifleur
#830
Eldegoss
#950
Klawf
#967
Cyclizar
#1019
Hydrapple
#641
Tornadus
Therian
#079
Slowpoke
Galar
#080
Slowbro
Galar
#199
Slowking
Galar