But since the user is asking for Vietsub, which is popular in Vietnam, the audience might be from Vietnam where access to international streaming services can be limited. Maybe there are legal Vietsub versions available. However, pirate sites also add subtitles, which is why users request Vietsub links. I should encourage using legal sources even if it's not in Vietnamese, maybe suggest dual audio options or other ways to access the show legally.
I should also consider that the user might be looking for a full feature article in Vietnamese covering the series, which could be a review, analysis, or news. If that's the case, there might be articles on Vietnamese websites that discuss "Black Sails" and provide links to watch it legally with subtitles. black sails vietsub link
In summary, the answer should guide the user towards legal avenues, explain the risks of pirated content, and offer alternative solutions to get the Vietsub experience they want. But since the user is asking for Vietsub,