Computer Search Removed
Eternal Unrest Added
Instant
Reveal Eternal Unrest as you draft it.
Immediately after the draft, you may add any number of cards named Sanitarium Skeleton to your card pool.
Reveal up to three cards named Sanitarium Skeleton you own from outside the game and put them into your hand.

Computer Search was a fun nod to the Pokemon TCG, but the mechanics don't translate well to MTG, where card (dis)advantage is much more costly. Even with madness effects, it didn't make up for playing a card that traded you 1-for-3. So let's do that in the other direction! This is a card that adds material to your hand that is good with other discard effects. It's one of my stranger effects, dipping into the conspiracy draft-matters pool.

Blooming Ritual Removed
Infernal Charge Added
Instant
Amass 3, then you may remove any number of +1/+1 counters from among permanents you control. When you do, Infernal Charge deals that much damage to any target.
Splice onto instant

Rituals are in a weird place in this cube. They can be strong, but games are not typically settled in single big turn plays. The spells decks have been more focused on consistent play than going off on a storm turn. I knew I wanted to keep a red splice card in the cube, but a ritual was not looking like the best showcase for the ability.

Ethereal Stalker Removed
Mesmeric Specter Added
2/2
Flying
When Mesmeric Specter enters the battlefield, create a Hypnotic Specter token.
Whenever Mesmeric Specter deals damage to an opponent, draw a card.

Ethereal Stalker was simply not what the UB deck wanted at 4 mana. The idea was ok, but at that cost, getting hit with removal was too much of a setback and other 4-drops were miles ahead of it. New card has a similar idea, but split over 2 bodies to make it better v removal and with flying as a more useful evasion ability.

Norn's Edict
->
Changed from a Council's Dilemma to be just you choosing the card type.
Now either destroys all permanents of the chosen type or exhumes the chosen type

Control decks that could use the old effect without getting hit by the opponent's choice were rare. Often you would be sacrificing some relevant enchantments just to cast your Wrath of God. To keep this as a sweeper that could hit more card types, the cost had to increase, and the reanimation option is a tiny bonus to make up for the extra cost.

Resurgent Phoenix
Whenever you discard a card, if you have no cards in hand, -> Whenever you discard the last card in your hand,

A wording change on the trigger to remove the intervening if so that effects which discard and draw can trigger it without making any confusing timings where you aren't sure whether you can get your phoenix back.

Absorb Essence Removed
Reality Refuted Added
Instant
Spell mastery — This spell costs less if there are two or more instant and/or sorcery cards in your graveyard.
Counter target spell. If that spell is countered this way, exile it instead of putting it into a graveyard.

We added another cantrip counter elsewhere, so changing this graveyard payoff to a cost reduction instead, and switching from threshold to spell mastery. Small reworking of the same ideas to help with the overall cube balance.

Faerie Jailbreaker Removed
Faierie Apprentice Added
1/3
Flying
Whenever a creature you control becomes the target of a spell or ability an opponent controls, you may draw a card.

I wanted a creature-protector that was a little more passive than Jailbreaker. Drawing cards instead of bouncing your own creatures in response to removal allows you to keep card advantage without slowing down to replay your old cards.

Cabalistic Tutor Removed
Rise of the Swarm Added
Enchantment
At the beginning of combat on your turn, you may discard a card. When you do, up to one creature you control gains lifelink and haste until end of turn.
Whenever you discard a card, amass 1.

I'm getting rid of the last card-negative tutor in the cube. We just don't do enough combos to deserve the slot. New card is a discard payoff and madness enabler. Wording is carefully done to allow you to give haste to your army token if you create it from the discard trigger.

Shaman of Decay
3/5 -> 3/3
When Shaman of Decay enters the battlefield, you may put target card from your graveyard on top of your library. -> Morbid — When Shaman of Decay enters the battlefield, you may put a card from your graveyard on top of your library. Then if a creature died this turn, draw a card.

To make the Fate/Miracle effects matter a little more frequently, I'm buffing the ETB of this one at the cost of some stats.

Nightmarish Delusions Removed
Unwelcome Guests Added
1/2
You may play cards from your graveyard that were put there from your hand or library this turn.

Nightmarish Delusions was by far the weakest hand attack card in the cube, and rather than buff it, I'm trying out a madness payoff, a kind of Containment Construct ish card.

Soula Runescribe
Added vigilance

I'm normally averse to giving creatures with tap abilities vigilance, because I like the tension between deciding to activate and deciding to attack. However, for the setup that you need to make the Runescribe start doing its thing, I don't want the 3-power flier to be the main role it plays without allowing it to showcase such a unique ability.

Chain of Denial Removed
Spellsnatcher Substitution Added
Instant
Create a 1/1 blue Wizard creature token with “, Sacrifice this creature: Counter target noncreature spell unless its controller pays .”

Recycling the Mage's Attendant token to make something more fun and interesting than the card it is replacing, which behind the throwback reference was effectively just a counterspell with a minor timing restriction.

That's the end of the updates, and maybe the final update for this cube, unless I get inspired to revisit it. I have some other projects I want to put together which might get uploaded to cubecobra in the future.