Gastly took the form of a young maiden and had attracted many young men who arrived at Maiden's Peak. He allowed Brock and James to see it, and brought them to the Maiden's shrine. After a failed attempt at taking over Brock and James with his charm, due to being interrupted by Ash and co., he was revealed to have been a Gastly by Ash's Pokédex.
It battled Ash and co. and Team Rocket and easily defeated them using its creations. It disappeared after the sunrise as it hated sunlight. It was later thanked by the Maiden's ghost for keeping her legend alive, and it vowed to find her lover and tell her when he does.
None of Gastly's moves are known.