Responses
It's so hard to yaois with that atmosphere. But are you ok with a different genre? Those give off very similar vibes:
http://www.mangago.zone/read-manga/kuroshitsuji/
http://www.mangago.zone/read-manga/trinity_blood/
But if you really REALLY want a yaoi, then maybe those might do:
http://www.mangago.zone/read-manga/nekrateholic/ (a love-hate relationship between a vampire and a vampire hunter)
http://www.mangago.zone/read-manga/eureka/ (I haven't read it yet, but someone said in the comments that it's somehow like Vassalord)
*hard to find
Any recommendations for yaoi mangas that are similar to, or give the same 'feels' as Vassalord? Thanks!