There are three Sync plates in the zone in which you spawn in, roughly surrounding the spire location. You must take the plates by standing in hem until the "fence" that surrounds them is fully grown and white. When you hold all three plates, the spire grows. Once you have control of a plate, you don't have to stand directly inside of it. However, Praetorians (level 26 major minotaurs) will spawn, and can take control back. Losing a single plate will cause the spire to start to regress. Hold all three plates for around 2-3 minutes, and the spire will form. Note, of course, the vault of glass raid, is deigned as a six player encounter.