Continuing on with the MH2 additions, Liquimetal Torque and friends:

Colorless:

Normally this would come at the end of the list, but Liquimetal Torque does influence a few of the other changes so it get listed here. It's a nifty little artifact that, aside from functioning as a 2 mana mana rock, enables all sorts of shenanigans, from allowing Saheeli, Sublime Artificer to turn herself into a creature to the simple Reclamation Sage destroying your opponent's creatures. I love shenanigans, so this is a great addition. Unfortunately, that means a card must leave. In this case, Lupine Prototype. While I love this card, it just doesn't stack up like it used to, and pulling it alongside Tolsimir, Friend to Wolves or Master of the Wild Hunt to turn it into a Doom Blade variant seems too unlikely and too low impact to be the sole reason to keep it in.

Blue:

First and Foremost we have a new card to interact with artifacts, Thieving Skydiver. It's artifact theft on a body that snaps on the equipment that it steals, what's not to love? Coming out is Meloku the Clouded Mirror, who does fantastic work in a less supported archetype or as a relatively straightforward win condition (play 5 drop, make tokens, attack for lethal). Meloku isn't gone for good yet, but it will be taking a bit of a break.

Not so much artifact related as just a good card, Svyelun of Sea and Sky is our second blue swap. Most of the text is trinket text, though there are a few Merfolk and changelings it can apply to, the relevant part is the 3 mana 3/4 that draws cards on attack. Good body for a decent rate that draws cards when it attacks and can block any of the 2 drops without dying if they aren't backed up with a combat trick, and a vast majority of the 3 and lower drops. Coming out is Shu Yun, the Silent Tempest. While Shu Yun's ceiling is remarkably high, the average case in this cube is simply a 3/2 for 3.

Black:

Black's changes are focused on the graveyard and making that a more accessible resource, as black isn't known to interact much with (opponent's) artifacts (Salvage Titan may be coming depending on how the cards play though, who knows what the future holds). The first of the graveyard interaction pieces is Unearth. It's a solid, cheap, reanimation spell. Easy to use and cycles away if unneeded.

The second card is more for the aristocrats deck, Nested Shambler. Garrison Cat in black, except it scales the number of tokens it can produce with any sort of anthem buffs or equipment you may have, and the tokens produced are Swarmyard friendly as opposed to Mayor of Avabruck friendly.

Blacks removals are a few of the more lackluster high cost creatures. Voldaren Pariah has never flipped, the 3 creatures necessary being too taxing in most games, and the Madness never finding relevance (triple black is a rough ask). Archdemon of Paliano is a decent card in the "black flyer with downside" club, but just isn't beefy enough to keep up with the other members, even if the drawback is unique.

Red:

I like phoenixes, you like phoenixes, and Rekindling Phoenix is an absolute beast of a phoenix. No cost to return on a solid body. Coming out is the infrequently cast Treasonous Ogre.

Green:

Just the one swap in green, another Reclamation Sage effect to go with our new necklace, Masked Vandal comes in. Vandals also has the benefit of changeling allowing it to get all the incidental buffs off cards like Svyelun, Earl of Squirrel, and Mayor. Genesis Hydra was chosen to leave due to being a solid green card that was mostly without synergy. Perfectly acceptable, but nothing that pulls you very hard.

Multicolor:

Sorin, Lord of Innistrad never feels good to play. The tokens are fine, but 1 toughness hurts as a 4 drop, and the emblems don't help you stabilize. Great offensively, but Orzhov 4 drops aren't the best slot for that. Orzhov wants a bit of lifegain and stabilization on 4+. Kaya, Orzhov Usurper grants lifegain and token removal at 1 cheaper.

I'm going to miss Sentry of the Underworld. It's got good art and is the only creature with regeneration that can both attack and block flyers. That said, the mana requirement to the regeneration is painful. Hopefully Liesa, Shroud of Dusk will be able to stave off flyers in a similar manner with the beefy lifelinking flying body while still pulling a good Ruric Thar, the Unbowed impression.

Our most inhuman walker to date, it's Grist, the Hunger Tide, the insect swarm! And what a walker it is. 3 relevant abilities and an entirely unique static that opens so many interactions. Sorry Varolz, the Scar-Striped, your role as the 3 drop for the sacrifice synergy deck has been ursurped.