The "Wraith" family is a speculative family, which has not been confirmed to exist and a sub category of the Unknown Family. It appeared in Pikmin 2,Pikmin 3 and Pikmin 4, and consists of the Waterwraith and the Plasm Wraith.
Waterwraith[]
The Waterwraith is a boss that made its debut in Pikmin 2 and Pikmin 4 It can only be defeated by Purple Pikmin; however, the entrance to the Submerged Castle is flooded, making them impossible to bring along.
Its appearance is generally humanoid in shape, with the suggestion of a head, body, arms and legs, but without distinct characteristics, as it has a watery, transparent body. The Ship notes that although it can be seen, its sensors somehow detect nothing, leading to the conclusion that the Waterwraith's physical form is anchored in another dimension.
Plasm Wraith[]
The Plasm Wraith is the final boss of Pikmin 3. It is responsible for capturing Captain Olimar. It is presumed to be an incarnation of PNF-404 itself. It is a virtually featureless, vaguely-humanoid Waterwraith-like being made entirely out of a cellular protoplasmic mass, which allows it to split different parts of its body off to create other semi-independent entities. It is fought in the Formidable Oak.