This is a Set Cube built entirely from cards that originated in or have appeared in a Core Set. Core Set limited is some of my favorite limited and I've aimed to try and replicate that feeling here.
Tempo decks are my personal favorite way to play blue. Build a board of evasive creatures and keep your opponent off balance with counterspells and board interaction. The Fliers archetype is perfect for a Core Set cube because there's been so much support for it, especially in recent years. Fliers have been good in limited since limited was thing and I don't expect that to change much here.
I say Fair Reanimator here because we're not looking to bring back a bomb on turn two. This is a control deck at heart that likes to draw cards, discard them for value, and ultimately win by bringing back a powerful creature.
Rakdos doing what Rakdos does. Sacrifice your own creatures for value on the board, then bring them back. Take your opponent's creatures, get in an attack, then sacrifice them. Between red's abundance of fodder and black's recursive creatures, this deck can go aggro or it can grind out the game.
Gruul midrange beatdown is another deck as old as Magic itself. This deck wants to out creature its opponents. Mana dork into three drop, into four drop, and swing for the fences. Back those threats up with burn and pump and you're playing with a classic.
Bring out the dice. This deck wants to take advantage of effects that can make its creatures bigger and effects that provide value for doing so. Build a board and accumulate that sweet value while you do it. Then trample on over for the win.
Gain all the life; get all the triggers! This deck is looking to grind. Gain enough life to keep your opponent's threats at bay, all the while making your creatures bigger and perhaps even draining your opponent out in the process.
Play with your dead things. The graveyard deck wants to benefit from discarding cards, sacrificing creatures, and anything else it can do to get cards in the 'yard. It's looking to bring stuff back to use it again. And again.
The ramp deck wants to do big flashy things and it wants to do them fast. This deck plays two to three turns ahead of its opponent, playing three drops on turn two and five drops on turn three. It uses its mana advantage to apply all the pressure it needs to get in for the win.
Get rewarded for simply playing Magic. The spells deck tacks on a little extra value to everything it casts. Bounce the opponent's creature, but also make a 1/1, get a counter, maybe a scry or two. Not much can beat Cube Blue Red when it's doing its thing.
Can I get the tokens box, please? One of my favorite archetypes, the go wide deck just wants to swarm the board with little dorks and turn them sideways. Make seven or eight tokens, then swing in and pump for the win.