It's the free reward from the Year of the Dragon event. I HIGHLY doubt they would give everyone access to it through a reward vendor, and then remove it on the 26th even if you claimed the reward. That would escape all logic, and wouldn't even benefit them from a monetary standpoint. Perhaps
@SteelStar or
@Cordovan could confirm for clarity sake but I would venture to say it's permanent as long as you claimed it on that character during the free month.
Edited: Clarified it's YoTD event, not Anniversary.