EV-33 Dragonrider is a Legendary Green Sparrow, one of four Sparrows first revealed in the Halloween update. The "Halloween Sparrows" are currently the only Sparrows with the Destabilizers talent. In a Bungie Weekly Update, DeeJ teased at how one of the sparrows would be acquired. Guardians who pre-ordered The Dark Below received the EV-30 Tumbler.
"Did you acquire a Destiny collector's edition that included an Expansion Pass? Did you acquire an Expansion Pass separately since then? If you have, we've got a special surprise for you. If you have not, but think you might still help yourself to The Dark Below, you'll also be invited to enjoy."
"When it lands, we want there to be no doubt that this is for you, and that you'll have a chance to enjoy it first. We want to make sure that you traverse the next leg of your journey in outrageous style."
Note: The EV-33 Dragonrider was originally called the S-33 Dragonrider in the data.