19.
Yamask has the word yama in it, meaning deity of death. Yama is also a god in both Hinduism and Buddhism responsible for law and punishment in the afterlife. I find this interesting because it makes me think Yamask is being punished to remember its past, like it did something wrong and is forced to bear the guilt. Even the Galarian version hints at this, as to evolve it must take at least 49 damage. In Buddhism, bardo or antarābhava is a concept of purgatory that lasts 49 days. What happens during those 49 days? Maybe you must atone for your sins, and Yamask's atonement is to remember its face.