Diamond & Pearl series
Ash caught Gliscor as a Gligar in Riding the Winds of Change!, as it along with many other Gligar and a Gliscor, had become trapped in a city after being blown there by a violent windstorm. Gliscor's attempts at using sonar to navigate out of the city were blocked by the tall buildings, and only served to attract more Gligar and the Pokémon soon formed a pack.
The pack survived by picking fruit from trees and stealing food from humans. After Ash and his friends helped the pack, Gligar decided to travel with Ash, allowing him to capture it.
In The Bells are Singing! Gligar was practicing gliding with Ash, but it made a wrong turn and accidentally crashed into a boulder. Shortly afterwards, it started being really clingy to Ash, making him recall it. Later, Gligar was used against Buneary to show Francesca how Pokémon battles work.
In Chim - Charred!, after a brief talk and recap, Ash and Paul decide to have a battle, and Gligar volunteers to be Ash's first Pokémon. However, Gligar's sheer determination comes to a screeching halt when Paul sends out his first Pokémon: Gliscor. Initially intimidated, Gligar pulls itself together and goes in for an X-Scissor, but Gliscor puts the breaks on Gligar with a Knock Off. Gligar recovers and uses Sand Attack, but Gliscor, unaffected, flies up and prepares a Guillotine attack. Gligar attempts to counter Gliscor with Steel Wing, but Gliscor's attack prevails and defeats Gligar. Initially sad, Gligar becomes elated after being congratulated for effort by Ash and the rest of his Pokémon.
It evolved into a Gliscor in Fighting Fear with Fear! in order to save Ash from a fall. It used the Razor Fang Ash received from Gary after Gligar had a practice battle with his Umbreon. It appears to have kept its personality traits even after evolution, as it still cries when scolded by Ash and also winks and sticks its tongue out.
Since evolving, Gliscor has been used in more battles. In Aiding the Enemy, Gliscor was used as a sparring partner by Torterra to help illustrate how Grotle could deal with its reduced speed. In Barry's Busting Out All Over!, Gliscor battled Barry's Roserade and the battle ended in a tie with Gliscor using X-Scissor and Roserade using Poison Jab, with both Pokémon knocking each other out at the same time. In A Breed Stampede!, Gliscor learned Fire Fang after being hit by an Ice Shard from Piloswine, and is revealed to have learned Screech some time off-screen.
In Dealing With Defensive Types!, it was Ash's third Pokémon in his battle against Byron and its first Gym Battle, it went up against Bastiodon, it first used Steel Wing from behind but Bastiodon countered with Iron Defense, its Fire Fang was countered by Flash Cannon. After dodging the first Iron Head, it was hit by two more in succession. It then cleverly used its wings to dodge Flash Cannon, it then landed on Bastiodon's back, although Bastiodon struggled, Gliscor was able to hit two Fire Fangs before being shaken off. Gliscor then knocked Bastiodon over with its tail. Its X-Scissor was overpowered by Iron Head. It then hid behind a rock which was broken by Iron Head, but it used this opportunity to attack from the air, however Gliscor was forced to dodge a Flash Cannon and it used Sand Attack instead to blind Bastiodon, it then finished Bastiodon off with Fire Fang, winning the match for Ash and earning him the Mine Badge.
In Sliding Into Seventh!, it was Ash's third Pokémon used in his Gym Battle against Candice, where it went up against her Snover. After dodging her Razor Leaf, it hit her with a super effective Fire Fang, it then knocked her with its tail. It was then hit with an Ice Beam but dodged a second one. It went for a Fire Fang but was hit with a Bullet Seed and was then knocked out by Icy Wind.
In Pedal to the Mettle!, Gliscor battled Paul's Torterra in Ash's full battle against Paul. Although it was able to cause a good amount of damage as well as using its speed to dodge Torterra's attacks, it couldn't escape Giga Drain, as a result being weakened while Torterra's health was restored. Ash then decided to recall Gliscor, only to use it again against Torterra later on, where it was defeated after being hit with Frenzy Plant.
In Mastering Current Events!, Gliscor battled against McCann's Scizor and lost. After training with Ash it challenged Scizor to a rematch. During the battle, Gliscor learned Giga Impact, and although it improved overnight, it eventually lost. Ash then left Gliscor with McCann for further training. It returned to Ash's party in Working on a Right Move! for its Trainer's battle against Paul in the Lily of the Valley Conference.
It was seen training alongside Ash for his upcoming battle against Paul in Familiarity Breeds Strategy!, where it was revealed to have grown significantly during its time with McCann. It was also shown to have perfected Giga Impact in a practice match with Dawn's Mamoswine. In A Real Rival Rouser!, it battled Paul's Ninjask and was shown to have learned Stone Edge while training with McCann. Unfortunately, it was not enough to defeat Ninjask, and so was recalled when it began to show signs of tiring. Ash sent it out again against Paul's Drapion later in the battle, where it was shown to do quite well, hitting Drapion with a powerful Giga Impact, then attempting to strike it with X-Scissor. McCann's training showed in this battle.
In the following episode, Gliscor put up a tough fight against Paul's Drapion. Even though Drapion had knocked out three of Ash's Pokémon, Gliscor was able to defeat it by burning it with a Fire Fang. It continued battling against Paul's Electivire. Although it had a type advantage, Gliscor had taken a lot of damage from battling Ninjask and Drapion, so it was defeated after getting hit by pieces of terrain launched by Electivire's Thunder followed by a powerful Brick Break.
Following the Lily of the Valley Conference, Gliscor was sent to Professor Oak's laboratory.
Best Wishes series
Gliscor was reunited with Ash in The Dream Continues!, where it and the rest of Ash's Pokémon posed in a group photo with him.