|Mane||Silver with a single green streak going through it.|
| Cutie mark|
Cone shaped beaker with a green fluid inside.
Catalyst is a unicorn scientist whom Underdog rescues from a group of raiders in Fallout: Equestria - Underdogs. She enters the wasteland after being exiled from her home stable and becomes Dog's companion upon her rescue.
Catalyst is a unicorn, born in her home stable. She grew up in the safety of her home, earning her cutie mark and going on to become a scientist. She was exiled from her home and decided to try and make a living out i the wastes, where she was kidnapped by raiders.
Catalyst was rescued from the raiders by Underdog, before they could inflict any of the graphic horrors they were discussing on her. Catalyst is ecstatic at seeing Underdog, confusing him as he expected fear. She immediately begins examining Dog, whilst spouting off numerous scientific theories. She accompanies Dog into a nearby shop, which the raiders were operating out of and encounter a griffin raider, who Dog buries under a shelf.
Underdog and Catalyst rescue an earth pony stallion named Antiquity, she is instructed to get to safety when Dog realises the griffin is not dead, but outside waiting. Catalyst moves to a safer distance, but returns to help Dog, using a knife, which she throws telekinetically, injuring the griffin's wing. Afterwords, Catalyst and the group make camp briefly and then arrive at New Chevalin, where they witness a public execution.
Underdog - She is fascinated by the good-hearted Hellhound, finding his appearance and ancestry interesting. She also appreciates him saving her life and is growing to like him as a person.
Catalyst is a unicorn mare with an electric blue coat and a silver mane with a green streak running through it. She wears a lab coat and a pair of goggles that cover her eyes. Her cutie mark is a cone shaped beaker with a green fluid inside.
Catalyst is a scientist at heart, infinitely curious about exploring new fields of research. She finds Dog fascinating, given he is a descendant of the heavily mutated Diamond Dogs and is utterly alien when compared to ponies and other pre-war species. She is also quite oblivious to the dangers of the wasteland initially, trying to strike up a friendly conversation with riaders who were arguing over cutting out her tongue.
Catalyst is an experienced scientist with her own methodology. She is also a powerful telekinetic and can use her own scientific knowledge to apply precise force with her telekinesis.
Catalyst wears a scientist's lab coat and a pair of goggles over her eyes. She also has a pair of saddlebags for carrying her equipment.