Demonic Tutor is a restricted card.
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If anything, I would take the orb out. I have it in my deck because I used to play against a lot of players that ran Armageddons. I find the deck does work quite nicely. I think I need more counter however.
Thank you for the comment. Looking back, I did play tainted aethers. I do wish to keep the deck monoblack however because I remember the ensnaring bridges working wonders against creatures as well as the banishings getting rid of things such as killer bees that get past the bridges. I think I also played extinctions.