The new rare mount is called Gromdrag.
It is a 4 step mount since there are 4 different pieces for it. First 3 pieces can be found in the caskets we get by completing 3 new deeds in Events-->Rewards For Accomplishments tab.
The chests require different deeds, they are listed below with explanations:
Combat Prowess reward requires players to take part in battles in the battlefields, chaotic battles and hand of abyss (levels 11-15)/hand of the sky (level 16+) as well as winning great battles and killing enemies in battlefields. By doing these, players might get +1 point for the deed. In short, players have to do PvP to be able to get this deed done and the first piece of Gromdrag Amulet by opening the casket received from this deed.
Huntsman's Ardour reward: In short, players have to hunt or gather resources under certain effects to be able to get points for this deed. Rainbow Power/Vertsida's Fury, Ulleriuni/Irriqudo or any other amulet that increases the probability of receiving Triads give the players a chance to get +1 point for this deed. When the deed is done, the player might receive the casket and by opening the casket, receive the second fragment.
Fortune Hunter reward: This rewards is done by getting points via playing luck games such as Magic Mirror and Luck glow or by opening mithril chests, precious caskets and chests as well as contraband bags. By doing these, players have a chance of receiving +1 point for this deed. When the deed is done, the player can get the casket and third piece of Gromdrag amulet from the casket.
Please note that all of the deeds I listed above require the players to get 1000 points for them to be able to get the deeds done. First 2 deeds are different than the last deed. If a player didn't get any points during the day for the Combat Prowess reward, for example, he/she is more likely to get points in the upcoming PvP battles in the battlefields i listed above. Same goes for Huntsman's Ardour reward, if they didn't get any points for that deed in the day, they're more likely to get points in the upcoming fights (or resource gathering) within that day. However that's not the case for Fortune Hunter reward. The chances are static, they don't depend on how many points the player received within the day.
The 4th and the last piece of the Gromdrag amulet can be received either by opening caskets and receiving it as a rare prize or by playing Magic Mirror.
These are the steps to receiving the new mount in the game.