Dimension seeding

Dimension seeding was an invasion method used by the Cybermen of the Cyber-Mainframe to form bridgeheads into parallel universes and begin converting their inhabitants, (AUDIO: Code Silver) as part of their campaign to upgrade the multiverse. (AUDIO: Master of Worlds)

Instantaneous conversion
Dimension seeding began with the translocation of dimension bridge technology, which resembled a highly advanced virtual reality headset, across dimensions into a parallel universe. (AUDIO: Code Silver) Once an individual used the headset, part of their consciousness was separated from their body and transmitted to a planet conquered by the Cybermen in a parallel universe. The cyber-converted lifeforms of these planets would attempt to attack the individual so as to use their mental avatar to form a dimension bridge to the parallel universe that their body was located in. Upon being attacked, the individual's consciousness would be returned to their body shortly before undergoing partial cyber-conversion. A dimension gate would then form as the dimension bridge created from the individual's consciousness connected the two universes.

Conversion over a dimensional gap
However, if an individual had used dimension bridge technology for an extended period of time (AUDIO: Telepresence) through an alternate means, such as a virtual reality game adapted from the original programming, (AUDIO: Game Theory) they could be cyber-converted and used as part of a link between universes, although the conversion would take significantly longer than through direct exposure to the dimension bridge technology. (AUDIO: Telepresence)

Securing a foothold
From here, the Cybermen would attempt to secure a foothold in the new universe, starting with the general vicinity of the dimension gate, the endpoint of the dimension bridge. This process involved the Cybermen deleting the majority of the lifeforms in the immediate area whilst using mobile conversion units to gradually increase the Cybermen's numbers. Once the area was secured, the Cybermen would begin to spread across the planet, converting the rest of its inhabitants and securing further stronger footholds until they had eventually converted the entire planet. After this, full dimension seeding would commence, which involved the Cybermen travelling to, and converting, further planets in the new universe, repeating their invasion methods until the entire universe was converted. (AUDIO: Code Silver)