Amnion are fundamentally different from any Earth creature - particularly humankind - in their mental and emotional structure. Physically they are humanoid: the Amnioni with whom first contact is made is described in "Forbidden Knowledge" as "a humanoid sea-anemone with too many arms." Amnion are however severely different from each other in physical appearance, with differing numbers of limbs, eyes, and other organs, as well as varying vastly in size and shape. This physical individuality contrasts with their mental identicality - their mentality can be likened to that of an insect hive. They are analogous to the Borg in the "Star Trek" universe, both in their collective intelligence (or "mind union") and in their aim to conquer through assimilation (turning humans into members of their own species).