A mount exclusively available for all those pre-ordering the Collectors Edition of Tera Online. News on the web is that this mount will no longer be available after the games release on May 1, 2012.
Again, the White Stallion Mount is only available via pre-ordering any edition of Tera Online. Same as the Regal Frostlion, the mount will only be available from now till the games release date.
To summarize, if you want any of these 2 mounts, go and pre-order your Tera Online game now. I’m sure there are more mounts that can be found in the game, but these 2 mounts are only available for people who pre-order. Here’s a full reference to Tera Mounts that might be interesting.