From Guild Wars 2 Wiki
I just added that you can get the black lion key, I did just get one from one, I added it for now, but if someone else could verify, that would be great.
- Any monster in the game can drop one, that's why we don't bother listing it on every monster's page in the wiki. —Dr Ishmael 01:37, 7 October 2015 (UTC)
Ok thanks for letting me know.