Angels, Demons and Knights
Champion of the Parish: A solid creature that will scale with the rest of your early game creatures.
Knight of the White Orchid: 2/2 knight with first strike is already powerful but the effect is strong enough to make it a good play later on as well.
Knight Exemplar: 2/2 first striker that is going to make your early-game work, this card boosts all of your other knights by 1/1 AND makes them indestructible. Essentially creates you a knight wall that will slow the opponent down, waste their removal or help protect your tougher creatures that will be coming out.
Mirran Crusader: Incredibly powerful 2/2 double-striker with good protections that already make it hard to remove. With Knight Exemplar this is a 3/3 double-striker that is downright painful to get rid off as well as being powerful in combat.
Desecration Demon: Easily one of my favorite demons, 6/6 demon with flying. Stupidly powerful for a 4 drop, the downside isn't even that bad for a demon unless you're against an aggro deck or token deck. Against aggro this card can be slowed down but once you get 2-3 of these guys out they will run out of creatures to sack into them and you will be left with buffed up demons. Against token decks these guys are expensive paperweights.
Gisela, the Broken Blade: Maybe one of my favorite cards ever printed. This baby is only with 4/3 of stats along with flying, first strike and lifelink. For all of your cards that are going to make you lose life this is going to get you that life back along with beating down anything else that dares fly on the battlefield.
Bruna, the Fading Light: For you certainly are not getting the most value for mana, but what you are getting is an alright effect along with a tanky angel. But what you're really getting is some flavour to go with Gisela, the Broken Blade. The card may not be good but it can merge into a 9/10 that limits what your opponent can play and will likely be the final nail in their coffin. It is important to keep in mind that this is a big target for removal so be wise when playing it against control decks, but against less control heavy decks most of the removal they will pack will be roughly 3 mana.
Lord of the Void: Very powerful demon that is perfect for a late game finisher for that opponent who refuses to GG. For you get what might be the most moral crushing cards in the game. A 7/7 is powerful but you already get 6/6 4 drop, but this card has an effect that lets you mill your opponents hopes and dreams away and then take said hopes and dreams and use them to bolster your late game and finally finish them off.
Instants, Sorceries and Enchantments
Thoughtseize: Perhaps one of the best black card for taking out your opponents threats before they even show themselves. and 2 life is a small price to pay for knowing what you're facing and being able to take out key components of your opponents strategy.
Doom Blade: Decent removal, is a cheep price to remove any problematic non-black creature. if you vs a black deck you will need to rely more on Mirran Crusader and Hero's Downfall.
Read the Bones: Like Sign in Blood except you pay and 2 life for the privilege of not drawing unneeded cards.
Stasis Snare: An interesting card for the affordable price of . This card can be useful in a pinch when you want to save more powerful removal for something more deadly.
Hero's Downfall: For destroy anything that's giving you a hard time. Useful to save it for when your opponent brings out their Planeswalkers.