Zoyd, also known as Soid (ソイド Soido) is a recurring enemy in the Darius series.
The Zoyds appear as a floating tank of sorts. They come in packs of six on a straight line or with three on the bottom and three on top racing towards the left of screen. When the reach near the left screen they turn around and go opposite of respected direction (up to down or down to up) then coast down or up. They take quite a few hits so keep your distance.
In G-Darius, a stronger variant of the Zoyd can be found on the later missions.