Hail a griffon tamer at any of the towers in Thundering Steppes. They will want you to find a griffon egg near the griffon areas on the west side of the zone. The griffon eggs are ground spawns call "a clutch of griffon eggs". They are harvestable nodes.
Once you find and harvest one, you have 5 minutes to take the egg back to a griffon tamer for the reward, the ability to fly between the available towers in Thundering Steppes.