The recently-revealed Alolan Grimer is a Poison/Dark-type Pokemon. As the population of the Alola region increased, dealing with garbage became a serious problem. As a solution, Grimer were imported from other regions and fed primarily on garbage, so their body composition changed—as did their form. What appear to be teeth in this Pokémon’s mouth are in fact residual toxins from the garbage it eats, which have hardened and crystallized. There are more than a hundred Alolan Grimer in Alola’s garbage-processing plants.
Also a Poison/Dark type, Alolan Muk evolves from Alolan Grimer. The Muk in the Alola region produce and store their toxins within their bodies so, unlike Muk in other regions, you won’t detect any unpleasant aromas when you draw near one. Alolan Muk has the same poisonous crystals as Alolan Grimer, but they are all over the surface of its body. Alolan Muk uses them to attack, just like other Pokémon use their fangs or claws.
Pokémon Blog 
I guess you could say that this will make breeding with gardevoir all the more interesting! :3
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