Griffon Towers provide rapid transit within many zones and, with GU56, some inter-zone transportation. Some zones require you to perform a quest first to obtain griffon access for that zone. As of GU56 you no longer have to quest or first discover a griffon tower to use it. Those quests are still in the game, but optional.
With GU57 in most zones all griffons connect to all other griffons in the same zones.
|Game Update #57
As of August 14, 2010, on Test, Timorous Deep Griffons did not connect to all other griffons in the zone. See the individual griffon pages for connections.