I understand that there's a manga of "Despera" by Yoshitoshi ABe.
Does anyone know where I could download all the issues in English?
Its "Wikipedia" article says that there is a serialized "graphic novel" by the magazine "Animage".
Not sure where you're seeing that. The wiki for Despera lists it first as an anime for some reason, the second listing says light novel. Maybe a typo on the wiki for whatever language you're reading it in.