The brothers' war

Airlift Chaplain
You'll never hit a Plains, but you might hit a creature or at least make it a 2/2

Calamity's Wake
Being able to just blank the graveyard to end shennanigans is an option

In the Trenches
The mana sink late game is interesting to consider

Kayla's Command
Commands are awesome, but this searches the library. If your table ignores that option, this is a fun card. Otherwise, not something to consider for Cubelet.

Loran of the Third Path
Great ETB effect and the politics of having your an opponent draw a card with you is always fun

Soul Partition
A unique "removal" spell that could replace an Oblivion Ring or so something similar.

Steel Seraph
Might be just a tad too strong, but worth trying. Flying can be particularly strong.

Teferi, Temporal Pilgrim
Very cool planeswalker if you play with them in Cubelet

Urza's Command
Commands are fun, the options here are all fine.

Arcane Proxy
This is pretty neat at either the prototype or full level

Combat Courier
A neat inclusion in a Pauper or One-Drop Cubelet

Surge Engine
A Figure of Destiny like creature is a lot of fun for Cubelet and this is no exception

Gix, Yawgmoth Praetor
Creates a neat political atmosphere and not free unlike Edric.

Gix's Command
Commands are great for Cubelet and the options here are neat.

Gixian Puppeteer
This has potential depending on how much you draw cards to be too powerful, but the death trigger to replace it is a cool effect

Hostile Negotiations
What a card, this is what Cubelet is all about.

Phyrexian Fleshgorger
This is wild. Late game might be an absolute horror to try and remove, but as a prototype, very nice!

Transmogrant's Crown
The way Cubelet works, this is just an equip cost of 1, which makes it very interesting to consider

Brotherhood's End
If you have a heavy artifact Cubelet, probably nice to consider this as an optional wrath.

Feldon, Ronom Excavator
Neat effect, a 2/2 haste creature is nothing to laugh at either

Mishra's Command
Commands are cool. Lots of great options!

Visions of Phyrexia
This is an interesting card and will depend on how powerful those powerstones could be.

Fade from History
Another neat wrath, but just focusing on the enchantments and artifacts. If you cubelet is looking for one of these, this might be it.

Titania's Command
Just like Kayla's Command, it has an option that searches the library. Either ignore that option or don't play the card.

Rootwire Amalgam
Neat effect, prototypes seem fun for Cubelet.

Simian Simulacrum
Great value creature.

Saheeli, Filigree Master
Completely fine planeswalker if you happen to play them.

Skyfisher Spider
Kind of a wild card with the shared graveyard, the life gain might be too much, but worth trying.

Third Path Iconoclast
Neat for a spell caster Cubelet to get some advantage.

Liberator, Urza's Battlethopter
Slowly growing, this is seemingly a fine card.