Question about epic trial key

If you install one of the epic (Prophecies and Factions) trial keys on a Nightfall account, does it open Tyria and Cantha to existing characters, or can you only try new characters?

At first I took it for granted that it was the former, and I thought, "hey, when my Nightfall-only friend installs the key, I'll help her snag the campaign-specific heroes and some skills before it ends, then she'll have them on her Nightfall character."

On second thought, it doesn't seem like the kind of thing they'd allow, so I was just wondering.

i'm not too sure but i think you have to make a new account if you want to use trial keys or that my just be the nightfall buddy key not sure tho

On my buddy key when I got it, I was able to take my character from Cantha over to Nightfalls, and once the trial was over, I still had the drop down window for heroes. But I was able to take her to NF, without a problem.

So I think that it would allow you to take a character from NF over to Tyria and Cantha, however I do not think that those heroes would be viable afterwards.