Merpin was a female Carnivine Jared caught with the help of Ioanin in Part 24 of his Pokemon Y Nuzlocke series. Merpin never really got to do much, being caught and dying in the same part.
The main fight Merpin participated was against Furisode Girl Linnea, where she used Leaf Tornado, and then she was hit and killed by an Aromatisse using Moonblast.