Vaul buildings are based off a combination of Xel'Naga technology and innovations from all three major races in the Koprulu Sector.
Because of this, many of their structures share traits such as Plasma shielding and Psionic power. They do have one ability making them unique: Firewalls. This renders buildings immune to attacks like nuclear strikes and random biological agents. Assimilation of technology from the other races does come at a cost. Some Vaul buildings are Neutral once constructed and require Encryption to prevent being used by enemy forces.
Plug-ins serve to support basic and advanced buildings with new and unique abilities. Like Terran Add-ons, they need to combine before the effects can be used. If interfaced structure is destroyed, Plug-ins become dormant and neutral allowing them to be captured by any race's worker unit.