This update will be followed by one that adds four cards to each color, bringing the total nonland card count to 100.

Mangara, the Diplomat always felt a bit medium, it didn't really contribute much to the cube. Bennie Bracks, Zoologist synergizes really well with the cube, can come down as an aggressive threat, and scales into the later turns by drawing you cards.

Mimic Vat, as much as I love the card it's just a bit too cute. This cube needs a couple more board wipes. Things can easily get gummed up and when you're behind you feel like you're drowning. Nevinyrral's Disk should help clear things out occasionally.

Treasure Map is really slow. Scry 1 is not a lot of value, and often the back side is just ramp and not card draw. Mazemind Tome should help players that are behind as well as provide more immediate value when you need it.

Relic of Progenitus it cycles and deals with graveyards. It never really feels great to play though. Unlicensed Hearse will hopefully feel a lot better to play.

Bag of Holding is a fine card and could absolutely come back, but is a bit redundant with Currency Converter. Multiple times I have played the card on t1 and never activated it throughout the game. There is a lot more of an incentive to activate Reckoner Bankbuster. The card draw feels much better than the looting.

Filigree Familiar is just a little too low on the power level scale. Skysovereign, Consul Flagship should make much more impact.

Talrand, Sky Summoner almost always was ditched during opening card selection. It's just really slow and there isn't a guarantee you'll be able to get much value out of it. Often times it's just a worse 4 mana 4/4. Fact or Fiction is definitely on the stronger side. I hope this feels fine to play and doesn't slow the game down with decisions too much.

Spectral Sailor is just too low powered. You'd hardly ever activate it more than once in a game and the damage never mattered that much. Delver of Secrets let's you peak at the next card to flip and can be a real threat.

Koma, Cosmos Serpent too strong. This was the game ender. Almost every single game ended with this card or waiting for this card to show up. It has no play and was too hard to deal with. Hydroid Krasis can't be cheated into play with show and tell for quick games, and rewards you better for ramping. Krasis hopefully won't run away with games the same way Koma did.

Beledros Witherbloom was also too strong. This was a massive game ender, often times being followed up immediately by Koma in the same turn. Without the untap ability the card would be completely fine to stay, but the ability to follow up a good threat with other plays makes this too good. Rather than a threat I decided to replace it with removal. Maelstrom Pulse can deal with large armies of goblins or Luminarch Ascension Angles. It can also deal with pesky permanents that most other cards can't.

Soulherder, I don't think I ever saw it cast. I definitely saw the card, but it never really did anything. The replacement Staggering Insight I'm not too sure about. It could be a dud, but turning an early creature into a card advantage engine, or gaining life with a blocker when you're behind could prove this card useful.