The grand navy is an organization and the replacement of the magic council in arcane odyssey(obviously). The grand navy is a very strict group to join, restricting some cool features ao has to offer for example grand navy players can’t change the color of their ships and their colors will be dark blue white and gray.
This recent image shows the main base of the grand navy Silver Hold. After completing the bronze seas story events this is where grand navy players will spawn.
Silver hold has no bosses but has a npc named “Commodore Kai” he drops his saber which was described by a tester as “nothing special” and only going for a few common weapons.
Their are currently 10 different ranks in the navy each having their own unique uniform and requirement.
Influence
The server that your in has a visible server wide meter “Influence” this meter determines how often grand navy npcs and npc ships spawn on players with a bounty.
This meter can be increased when grand navy players claim islands arrest criminals and successfully hold executions. The meter starts out at 70 percent the higher it is the faster grand navy ships will spawn on notorious players and in affect decreases the rate criminal npc ships spawn on you. When the Influence meter goes below 20 percent the server becomes hell 
. Grand navy npcs no longer respawn silver hold is claimable and when claimed players get awarded the “Bronze Sea Abolitionist” badge. Immediately upon taking over silver hold you will be given 5 stars of notoriety. You can pay off your notoriety mid sea and if your about to die and you pay off your notoriety the grand navy ships will stop chasing you. But of course if you have bounty they will come after you.
Ah yes notoriety
Of course renown the new term for “reputation” is how npcs treat you and your threat level to other npcs.
Edit: Credits to @Shellseawing you cannot pay off your notoriety when taking over silverhold
