-4 altar reap
+4 Dash Hopes
-4 bumb in the night
+4 Feast of Flesh
[Dash hopes] is tecnically more useful then [altar reap]: I do need to draw more, but it's unlikelly to have a creature to sacrifice, or that I trade a creature. What I need, is to protect my infinite combo: it's actually hard to really protect an enchantment an artificat, but it's actually certain that everyone will take that 5 damage instead of let me play the combo, if they don't have two card to counter it.
In that case, he actually wasted two card to deal whit it. (the combo is a finisher)
[Feast of Flesh] is better than [bumb in the night]: it deal less damage, but it fetch life and can target creature.
[Deathrite Shaman] is better in any single way than [Perilous Myr]: it deal damage even in the oponent turn, it let you use the graveyard as resource, it counter card that can be replayed from GY, it's a one drop. It cost more money. He is too rare and good for the opposite to appean, and is a standard card. Soo, proxy. Even if the myr doesn't act nearly as a substitute. [Geralf's Messenger] is a bit costly too, actually is from where most of the price of this decklist come from: but he is simply too good to be dropped down. He is even better than the kitchen, and as we play mono black, it's incredibly easy to cast. But impossible to proxy or substitute. He is too good.
You can still not pick him up, but I woulden't recomend it, as he can work around some hate card.
In the maybe list there is some card that could work wonder into this decklist, BUT cost to much. They surelly work, and if you have more money to spent you could look at them and to some red/white splash for utility/land