Mmm, yes, this is what I meant:
http://www.wowdb.com/spells/100332-vicious-war-steed
That shows the three different achievement levels and you get a mount for each one. I got one on my priest but kind of stopped PvP'ing and my guild broke up before I got further into the achievements. I knew the second one could be sent to another toon and the third one was account bound. Looks like that might have changed.
Things got a little wonky when they added in the "saddle" token and ability to send account bound items cross realm and cross faction.