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all creatures in pokemon are either humans or pokemon so it's strange that they would add creatures that aren't human or pokemon (ultrabeasts)
although there is one other example of non-pokemon, non-human creatures in the series: zygarde cells. both were featured in the video. is it possible that zygarde cells are themselves ultra beasts? they are mindless blobby creatures.
now look at the collar on type:null. it has green hexagons visible on the spokes. type:null is made out of parts of other pokemon....but maybe it was given a zygarde core to give it life?