Quit this game long time ago. The system i remember was: Every guild that made damage to the crystal had chance to capture the territory.
No idea how the system behind it was since memory is tricky but this was a very fair system back then since small guilds could get territory in a equal manner to big guilds.
But we're talking about a private server that won't have the same p2w factor that we had on aeria server back then where all whales gathered on 2 guilds making impossible for small guilds to get a territory unless both got their territories first.