Saw someone looking like Gwen in Kaineng Center

Yesterday, in Kaineng Center, I say a player who looked exactly like Gwen and was also wearing her armor.
I assume this is a costume? How do you get it? I saw something about a Halloween event, but I got the impression that you don't get to keep the costume.

Thanks!

It's an Everlasting Gwen Tonic from the 6th year birthday gifts.
Not that expensive too!

http://wiki.guildwars.com/wiki/Everlasting_Gwen_Tonic

All the Everlasting Tonics have dropped in price. You should be able to buy a EL Gwen in the 50k range.

Yeah, guess they are not gw2 hom related and therefore people who have 6 year olds account in need of the points are selling them and not many people have been buying them. I have bought a few for that reason. I like them, don't need any HoM points (ended at 40/50 with no change of getting 45/50) and I won't need money either pretty soon.

But you should be able to get one for 35-50k atm if you want it.

Hmm but I suppose that if you use it once you can never use it again, right?

Everlasting, as in endless uses