Dusclops first appeared in As Luck Would Have It, Kirlia, where he was a wild Pokémon in the Battle Pike that Emerald had to fight. Dusclops teamed up with a Kirlia to inflict status moves on Emerald's team. Emerald was prepared for this however, and had his Pokémon shake off the statuses and defeated them. After Emerald finished his challenge at the Battle Pike he headed back through the rooms and calmed down the rampaging Pokémon, one of them being Dusclops, who was from Mt. Pyre. Dusclops reappeared in A Sketchy Smattering of Smeargle where it was revealed that he followed Emerald alongside a Sudowoodo to join Emerald's team. Both of them proceed to help fend off the Smeargle in Artisan Cave to help Emerald capture Jirachi. They later defend Emerald from an attack from Guile Hideout, which impressed Emerald enough to let them join him.
Emerald with his Dusclops, Sudowoodo, and Sceptile
In Sneaky Like Shedinja, Dusclops battled as Emerald's second Pokémon in his battle against Greta. Emerald had Dusclops use Psychic on Heracross, which gave him good marks on his scores in skill as well as mind and body. Dusclops was easily able to handle Heracross's attack due to Fighting moves having no effect on Ghost types. Due to this Heracross was unable to score enough points, giving Dusclops the win with a score of five to two. For her second Pokémon, Greta sent out Umbreon, which had an advantage over Dusclops. Umbreon attacked with a powerful Feint Attack, knocking Dusclops off balance. Emerald attempted to counterattack with Dusclops's Will-O-Wisp, but Umbreon easily dodged it and confused Dusclops with Confuse Ray, giving Umbreon the win with a score of five to one. Due to Dusclops weakening Umbreon, Sudowoodo was able to finish it off with one Low Kick, giving Emerald the win with a score of two to five.
During the Battle Dome challenge in Verily Vanquishing Vileplume II, Dusclops fought against a Vileplume and easily defeated it with Fire Punch, which Emerald taught to him with Battle Points. Dusclops also fought during his fight against Ruby and his Rara. The battle starts with Rara using Hypnosis to put Dusclops to sleep. He breaks free of the attack and attacks with a barrage of Shadow Balls. Surprised that Rara is still standing, Emerald has Dusclops use Fire Punch, which gives Rara a burn. Although Emerald thought that would help him win, Rara's AbilitySynchronize activates, giving Dusclops the burn as well. On top of Rara using Imprison to keep Dusclops from using Shadow Ball, both Pokémon faint from the burn, resulting in a tie. Dusclops was not used during his fight against Tucker due to Emerald believing he did not need his regular team to win.
In The Final Battle VI, Dusclops joins the rest of Emerald's team in an attempt to attack Guile Hideout. Guile easily fights them off and begins attacking them, which forces Emerald to realize he truly cares about Pokémon. Seeing the change in his heart Jirachi grants his wish to free the Pokédex holders from petrification. Soon after he was used to help stop Guile Hideout from escaping.
In Dusclops first appearance, he was a rampaging Pokémon that would attack on sight. After Emerald used his E-Shooter to calm him down he became attached to Emerald and followed him until he joined his team. He cares deeply for his Trainer, and once attempted to suck Emerald into a black hole to have him all to himself.