Mono Black Deck Build?

Well, it all depends on how much you want to spend on cards and format. you say its just casual but is it legacy casual, extended casual etc or just a bunch of friends playing no format casual. If its the last, i would replace the diabolic tutors with demonic tutors (or vampiric tutors. replace plague wind with damnation. replace raise dead with rise from the grave, and i would definitely play 4 dark rituals. very few things are as nasty as a 1st turn hymn to tourach (except maybe 2 first turn hymn to tourachs), but be aware most friendly groups look on that with the same warmth as a multi-player group welcomes an armageddon. I've tried not to suggest too many changes