Some of these were difficult. I'm going to break down my thought process so that when I inevitably swap some of these cards out (looking at you Skullclamp) I'll know why I put it in to begin with.

On paper, this deck should struggle with getting actually impactful creatures to reanimate. Your odd Doomed Traveler, Tithe Taker, and Spirited Companion aren't going to swing the game in your favor. On top of that, there's no way to sacrifice any of those three to reanimate them when you need to. The deck has 5 reanimators and 6 targets.

• Ministrant of Obligation is a bit high-costed so Restoration of Eiganjo won't hit it. That said, making two fliers instead of one is incredible, so in a game where you need that extra flying attacker over the long-term, this is a solid include.
• Skullclamp... is a busted card. That said, I don't think this is a particularly good deck. Compared to the most aggro of starts I'm not certain even clamp would save this deck.
• Altar of Dementia is a more fair sac outlet, and you can mill yourself to find more reanimator targets.

I think this deck is going to struggle with landing its 5-drops. These sideboard cards aren't incredible, but they give a slow deck a decent early game.

• Segovian Angel is a decent aggro flier.
• Emancipation Angel is anti-ramp, but if you need the body on turn 3 I don't think you'll complain.
• Angel's Grace buys you an extra turn in a cube full of crazy aggro swing-outs. And it happens to be extremely thematic. A pseudo-fog in a deck of big fliers can win you a game one- same trick probably won't work twice though.

Once again, I wanted these sideboard cards to focus primarily on the deck themes rather than cross-deck synergy. Where necessary, I added some removal, elsewhere I added some higher mv. bombs, and still elsewhere I added low-curve aggro threats.

Big Changes coming this update!
After playing with some friends, it was suggested that I try to add a 3 card sideboard to each deck. At first I dismissed this idea because the packs I keep the decks in can barely fit 21 cards, much less 23-24. It was out of the question. But the more I thought about it, the more I realized that increasing player agency was more important to me than the fluidity of packaging. So here are my sideboard cards for the blue packs.

While I add these, I'm not really considering synergy between other packs in the color like I normally would. Instead, I'm assuming that you're only siding in these cards because you want to enhance a particular gameplay experience. Generally, the sideboard cards will fall into the categories of making the deck "faster" or "slower."

• Ornithopter of Paradise improves the late game (letting you drop a 4 drop on turn 3)
• Faerie Mastermind speeds up the deck as a two drop, still has late-game draw power
• Deluge gives the deck that one extra combat late game + gives it an answer to big reachy threats like Elder Gargaroth

Trying to add interplay with stun counters, convoke is simply better than hitting artifacts

Banned in commander, balanced in cube :) The spellslinger decks have trouble having both creatures that benefit from spells and spells to cast, so I decided to add lutri as a companion for both of those packs. While I do think having a companion is definitely an advantage, I think spell-slingers need the help. In the future I might even reduce the amount of non-spells in these packs since they'll always have access to lutri.

I found that Kick in the Door venturing into the dungeon just once wasn't good at all, and it became a hassle for nothing. So I moved that to R-Heroic over Samut's Sprint. R-Counters now has Ordeal of Purphoros as it's heroic throw-in + removal.

Fresh Meat did nothing too often, since it relies on making a big swing and your opponent blowing you out, and you'll never hold up the mana for it if you could just make a bunch of tokens anyways. Toski, Bearer of Secrets is more interesting in combat, gives a reason to attack with 1/1 tokens, and draws cards if opponents let the damage through.