Have you thought about adding a possible Vampire's Bite? It can bump up Kiln Fiend by +6/+0 Since he gets his own bonus plus it is a one black instant.
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Have you considered putting Anowon, the Ruin Sage in possibly as a replacement for the Kalastria Highborn? There seems to be a theme with sacked creatures providing you with buffs. You could even consider taking out the just because only a few of your spells are red and there are some decent black ones that could still give you creature kill or life loss. Just a thought though. Great deck nontheless!