Board Thread:Theories and Speculation/@comment-1512913-20161119171442/@comment-25122992-20161129170730

It doesn't seem strange to me in any way. Their direct ability is that of merging 3 natures, there's no mention they could 2 of these components individually. Mei Terumi is a perfect example of a person with 3 natures (Earth, Fire, Water) and KG ability to mix some of them (i.e. Earth + Fire and Fire + Water), but these are the combinations she's limited with. She can neither mix all these natures simultaneously (resulting in KT ability) nor use a new KG combination aside from these two (i.e. Earth + Water = Wood). It's not like your theories and thoughts aren't possible, but I think this part excludes any speculation. The only natures Oonoki/Muu can merge together are Earth + Wind + Fire = Dust Release. Technically, they are limited with this and only this combination. They have the ability (KT) to use them simultaneously to create a combined 3-elements nature, but lack any of the abilities (KG) that would allow them to use 2 of these natures simultaneously to create a combined 2-elements nature.