Silvally first appeared as a Type: Null in A Straight Street to Rivalry!, where it appeared alongside its Trainer talking to some Team Skull grunts. It was later used to battle Lewis and Aipom and easily defeated Aipom after the latter's Superstar Swift failed to work.
Type: Null was Gladion's main battler during the Battle Royal tournament and was able to easily defeat its opponents. However, during the second round, Type: Null took some rather strong hits from a Trainer's Pangoro. On the advice of Nurse Joy, Gladion decided to rest Null for the finals.
It appeared once again in Conclusion of a Royal Bout!, where it observed its Trainer in the Battle Royal tournament finals. Despite the loss of its Trainer, Type: Null seemed satisfied with Lewis and Aipom's victory.
Type: Null reappeared along with Gladion in Crisis in the Gardens!, where it watched the battle between Lewis and Guzma. Upon Lewis' loss, Type: Null seemed concerned for Golisopod.
In A Team Skull Takeover!, Type: Null appeared alongside Gladion to confront Lewis after he had gained entry into the Shady House. In the following episode, Null battled Aipom once again, but was defeated after Aipom mastered the use of Superstar Swift. After the battle, Type: Null was seen to nod at Aipom, finally accepting the latter's strength.
Type: Null would battle Aipom once more in Breaking the Limits!, being used by a furious Gladion to battle Lewis after the latter allowed Lillie and Nebby to be kidnapped by the Aether Foundation. During the battle, Aipom's Focus Punch was able to crack Null's limiter helmet, temporarily stopping the Synthetic Pokémon in its tracks. Hearing Gladion's furious shouts to keep battling, Type: Null smashed its helmet against the ground, destroying it and causing it to evolve into Silvally. The sight of his newly-evolved partner calmed Gladion down and he stopped the battle in order to save Lillie.
Silvally was used by Gladion during his and Lewis' takeover of the Aether Foundation in Trouble in Paradise! and The Cracking Dimensions! While Lewis and Lillie were in the Ultra Megalopolis, Silvally helped to battle the Ultra Beasts invading Alola.
In The Calm After the Storm!, Silvally was Gladion's third and final Pokémon in his battle against Lewis. It went up against Lewis' Lycanroc and, despite putting up a good fight, was defeated by its Shattered Stormshards.
Silvally, along with Gladion, was seen watching the Alola League Lanakila Conference.
As a Type: Null, Silvally was seen to be a very serious Pokémon, rarely showing emotions. It seemed to hold Lewis and his Pokémon in high regard, as it was impressed when Aipom managed to win the Battle Royal tournament and was concerned by his defeat in Crisis in the Park! This seems to reflect Gladion's changing opinion of Lewis.
Upon evolving into Silvally, it showed a much more compassionate side to its personality, calmly reasoning with its Trainer to stop the battle with Lewis and to go and rescue Lillie instead. It was much more expressive than it was as a Type: Null, likely due to its limiter helmet being removed. It's power levels have also increased drastically since evolving, allowing it to go toe-to-toe with several Ultra Beasts at once.