Requirement: complete 2,000 duties via Duty Roulette: Mentor.
So basically you can't get it while casually helping people with roulette, you have to grind it if you want to get it in a reasonable time (less than a year), you need to do this roulette at least 6 times per day to get it in under a year.
I understand the idea of keeping a long term achievement for those who use mentor roulette, but I'm afraid this reward being a 2 seater mount will increase the number of bad mentors who ragequit as soon as they get something they don't want, people who will spam mentor roulette just trying to get easy clears like dungeons or hests. I don't think that was a good idea.
It also doesn't help that those mentors aren't held accountable despite the mentor status coming with a warning, so I hope that astronomical number doesn't finish killing the mentor status in instances, status that already carries a terrible reputation.