Unidus

A Unidus in Speed Highway (SA1).

A Unidus in Death Chamber (SA2).

E-32 Unidus (ウニダス) is an E-Series Eggman robot encountered as an enemy in Sonic Adventure and Sonic Adventure 2. It is an evolution of the old Orbinaut model badnik from the 2D Genesis games, and is often referred to by the same name depending on translation. Uni is the Japanese word for "sea urchin", and these robots live up to the name with their floaty, spiky attack method.

In Sonic Adventure, this badnik was simply known as "Unidus"; it was not until Adventure 2 that it was given an E-series numeral.

Sonic Adventure

The fourth variation of the Orbinaut model, it's most close in design with the Orbinaut appearing in Sonic 3. It attacks in two ways, either throwing their spike balls at its enemy or by sending them in arcs for a wide radius attack.

Character	Stage
Sonic	Speed Highway
Tails	Sky Deck, Speed Highway
Knuckles	Speed Highway, Sky Deck

Sonic Adventure 2

Now known as E-32 Unidus (ウニダス) in the Japanese manual, this Sonic Adventure 2 model is basically the same as the one in Sonic Adventure, but it won't throw its spikes, bustling around randomly instead.

Character	Stage
Tails	Hidden Base
Knuckles	Death Chamber