Black and Blue is a beatdown deck that plays large under-costed creatures that relentlessly pummel your opponent!
The deck aims to aggressively play under-costed creatures and to apply pressure on the attack from the get go, while essentially ignoring draw-backs of your own creatures. The plan is to win before the draw-backs make a difference anyway.
Creature clashes on the battlefield are normally advantageous with this deck as:
your creatures tend to be bigger than your opponent's, for the same mana value
it's ok to exchange your creatures for your opponent's in combat - as theirs, of the same size, normally cost more to play
you have cheap removal and combat trick spells to turn combat to your favour
Battlefield stalemates though can be troublesome and should be avoided.
The many versions of this deck are all basically made of three classes of cards: aggressive "heavy-hitting" creatures, utility creatures, and removal spells. The heavy hitters are the key element of most versions of this deck, with the number of utility creatures varying from version to version. It is quite natural then to look at these three groups as the main packages of the deck.
heavy hitters
utility creatures
removal
is what eventually kills the opponent. There's a lot of variety in this package across the various versions of the deck. However, the common theme is creatures with high stats (p/t) to cost ratio with neglect-able draw-backs.
These creatures will hit your opponent early on for some significant damage, trade-up with your opponent's creatures or absorb a removal spell. All good options, considering you most likely have more of these than your opponent has removal spells.
The heavy hitters package constitutes up to one third of your deck and normally includes 15-20 cards, like the old classic Erg Raiders (a 2/3 for 2 mana that damages you when it doesn't attack), Wanted Scoundrels (a 4/3 for 2 mana that gives treasures to the opponent when it dies), Moroii (a 4/4 flying vampire that makes you lose 1 life every upkeep - Juzam was good, right?), or Phantasmal Dreadmaw (a 6/6 trampler for 4 that is sacrificed when targeted).
Some creatures in this category can also generate value beyond combat... like Blade Juggler's card-draw ability when spectacle-cast, Dire Fleet Hoarder's Treasure token, or Labyrinth Guardian's embalm token.
this is what gives the deck staying power beyond the early game, in those cases where the game actually gets there...
The package includes mostly creatures which enable card selection, provide some card-draw, or provide evasion abilities to your other creatures. More rarely, the package can also include a few non-creature spells, like Snapback (an instant speed bounce spell that can be cast for free).
The utility package typically includes 4 to 8 cards. Examples include: Wharf Infiltrator, which offers card selection + can generate 3/2 tokens, Mogi's Marauder, which provides evasion , and Unwilling Ingredient's card-draw from the graveyard.
Some heavy hitters also duplicate as utility once the opponent gets rid of them from the battlefield. For example Cobbled Lancer's card draw ability from the graveyard.
rounds out the deck and it is primarily composed of instant speed removal or combat tricks with the occasional sorcery speed removal. Particularly interesting is the use of pump spells that can duplicate as both removal and utility that can sometimes accelerate the kill or generate extra value.
The removal package normally includes 6-8 spells in various combinations of pump/removal spells some examples of which are: Supernatural Stamina, Agony Warp, Reave Soul, and Essence Extraction.
Black and Blue is a consistent and fun aggressive deck with plenty of powerful synergies and a surprising staying power. The deck demonstrates the strength of a number of cheap creatures which, on the surface, may look weak.