Nava

Nava is a ghost Umbreon. Although generally share many similarities with the Umbreon species, there are a few key differences, most of which are physical. Aside from these differences, she has the same qualities as a regular Umbreon. 

One of the more notable physical variations is the colour of Nava's rings. Unlike the average Umbreon, Nava has light purple rings instead of yellow, though they can still glow during the night and at will.  

Her eyes are the same red colour seen a regular Umbreon. 

Another physical variation, and arguably the most notable, is the fact that Nava shares many qualities with other ghost type Pokémon; for example, she can materialize and dematerialize at will, as well as appearing solid or see-through, a trait observed by Pokémon such as Gastly and its evolutionary line. Form-wise, her main body is similar to an Umbreon's; her paws have little trails of wisp/plasma, which can be compared to the bottom trails of Mismagius's "arms". This trailing effect is also at the tip of her tail and ears. 

A less physical variation is Nava's dual typing, it being the Dark type seen in the Umbreon species and the Ghost type present in other Ghost Pokémon. Her weaknesses are a mix between both types, though this changes depending on whether she is solid (materialized) or semi-solid (dematerialized and see-through): when solid, her strengths and weaknesses match those of the Dark type, though fighting attacks are reduced to only regular strength; when in ghost forme, she takes on the strengths and weaknesses of the Ghost type, though she also becomes weak to Fairy attacks.