To receive this new turtle, the Mossy Tartagon, you want to buy the Verdant Maelstrom for one Dragon Tear and infuse it with a Dragon Quintessence to level it. You will need to either buy the Dragon Quintessences for 100 Dragon Tears each or look for Dragon Motes (green level or higher) and hope that they drop a Dragon Quintessence.
If you want this new turtle mount, hopefully you’re doing the weekly quest, The Matter of Motes from Rion Stantor. He stands to the left side of the middle statue right in front of Sanctum’s steps. He will give you eight of the Dragon Quintessences. Once you receive a Dragon Quintessence, infuse it with the Verdant Maelstrom, to do this simply click on the Verdant Maelstrom and it will eat the Dragon Quintessence. When your Verdant Maelstrom reaches level 50 you will receive a shiny new mount!
The Mossy Tartagon will scale with the speed of the fastest mount you own up to 110%.
And for those that want to see what differences there are between the normal turtle and this mossy turtle…