Bio-Dome

The Bio-Dome is a Vok-created structure, composed of a mixture of strange materials both organic and technological in nature. While outwardly it resembles a giant green dome, within is enough machinery and power to burn the surface off, say, a medium-sized moon. Through it, the Vok can also communicate with and scan invading life forms. It does not have a doorbell.

Beast Wars cartoon
Following the destruction of Brigadoon, the Vok received a signal indicating something was up on Earth. They dispatched an energy pulse back to the planet, and Rattrap and Airazor tracked said pulse to find a strange formation in an area of wilderness. Airazor tried to scan the crystal at the middle of the formation, only for it to blast her, then blast Rattrap, then create a dome structure, sealing in Airazor. Airazor recovered to hear alien voices, but when she tried to communicate, she was zapped by arcs of energy. While Rattrap and Optimus Primal unsuccessfully tried to cut their way in, Megatron and Scorponok arrived. Scorponok's toxic sting opened a hole in the side of the structure, allowing Optimus and Rattrap to enter. Rattrap hauled Airazor out, but Optimus stayed to try and communicate with the aliens.

Once the aliens had tortured Primal a bit with a full body scan, they manifested as the image of Unicron to talk with him. "Unicron" told Optimus that he, the Maximals and the Predacons had contaminated the experiment, and the termination sequence would begin. As Optimus broke free and smashed his way out of the Bio-Dome, it unleashed a beam of energy that struck one of the planet's moons, revealing it to be a massive weapon. Once the beam of energy finished its work, the Bio-Dome disappeared.