Talk:Weiss' Arma Gigas/@comment-2601:2C0:4700:752D:C578:3EDA:B1BC:E664-20180319210913/@comment-29644557-20190216071455

I think another reason is that (bear with me here) it isn't exactly a Geist. The manga calls it "an amalgam of smaller Grimm", meaning it could be an artificial, man-made Grimm made of possession-type Grimm Frankenstiened together (Geists being used in that mix). Considering we also see another possession Grimm in the form of the Tentacle Grimm and are assuming other possession-type Grimm can exist, the Arma Giagas (specifically Weiss' Arma Gigas) may be a hybrid type/species all its own. Mostly speculation, but possible.