Mimic Vat
It lets you play with your opponent's cards, sort of. Ideally you would grab something like a Diluvian Primordial and spam it till you drop, but it can also be used productively with many of the artifact creatures in this section. Remember, clones don't die at the end of the turn, they get exiled, so make a friend and have them block for you. It's good to get people used to doing what you say.
Echo ChamberAnother way to make token clones of your opponents' stuff, however in a much more limited and political way, and for more mana. It's best against people who don't run a lot of creatures, but run enough. And remember, the tokens are exiled, not destroyed, at the end of the turn.
Muse Vessel
Somewhere between disruption, card advantage, and a way to sink your tentacles into the sweet, sweet brain matter of your opponents. This card and cards like it is where the deck becomes itself. While there are usually better things to do with your mana than instantly make an enemy and start casting their cards, few of them are quite as much fun.
Ornate Kanzashi
Like a muse vessel, but you need to activate the card while it's still the turn you nabbed it. The best player to target with this is someone who just cast Imperial Seal or Vampiric Tutor. Following that is Timmy, because he isn't likely to have too many instants, and following that is someone trustworthy who has a Sensei's Divining Top or other topdeck manipulation and too many lands who you want to be pals with.
Clone Shell
'Ol Carl is a pure politics card. You know that he's got a Warping Wail under him, but the table is certain it's an Ulamog, so they'll never attack on the ground. Making a lot of him is also one of the best ways to dig through your library really fast to find whatever you need.
Mindless Automaton
This is an interesting card because it's sort of a looter, but also sometimes you just have way more cards in your hand than you know what to do with, and then he can get pretty big and he still ends up drawing you cards.
Pilgrim's Eye
One of the main reasons you run Wastes. It's also one of the only card-advantage neutral artifact creatures with flying, which is a plus.
Solemn Simulacrum
AKA the sad robo. One of the other main reasons you run Wastes. It's a good card.
Matter Reshaper
Sort of a mini Treasure Keeper, cheap and efficient card advantage is what this phase of the game is all about.
Treasure Keeper
Basically the definition of a hidden gem. Because this deck tends higher on the CMC spectrum, you have a good chance of hitting Junk Diver, Workshop Assistant and Myr Retriever, enabling you to cast him again to gum up the board and rebuild after a board wipe.
Junk Diver, Workshop Assistant and Myr Retriever
Your Eternal Witnesses, if you happen to be playing your deck and not someone else's. Junk Diver is the best of them because it can fly.
Scrap Trawler
Sort of like a lord for your Junk Diver and friends. It can give you a lot of card advantage, but it most of the stuff you want to fetch most is more expensive than what you can chump with or you have a sac outlet.
Ancestral Statue
Aside from the synergy with your commander, he allows you to reuse sad robo, Pilgrim's Eye and Sandstone Oracle, as well as re-spin Carl to find something better. You get swag points for returning something an opponent owns to their hand, then using it to kill them when you take control of their turn.
Cogwork Assembler
One of the lategame options this deck has other than what's in the "combo parts" section. It can be fun to clone a Treasure Keeper, but remember the assembled clone is exiled, so it doesn't trigger death effects unless you can get someone to block it for you.
Prototype Portal
I admit, the possibility of getting 2-for-1'd is real and frightening, but so is a Clone Shell every turn, especially when one turns into a Kuldotha Forgemaster and ends the game. Just one copy puts you even on card advantage, so if you deploy all your ramp before you cast it, there's a good chance you can activate it in response to removal even if an opponent is holding it up.
Mirrorworks
This card is bonkers, especially because it allows you to copy your ramp pieces, copy Ancestral Statue, and copy everything you bounced with Ancestral Statue, and copy everything you bounced with the copy. It's like playing two decks at once, which usually takes the amount of decks your playing to somewhere around 4.
Trading Post
Acts as a very strong sac outlet for cloned Treasure Keepers, and its other modes are situationally useful. With Mirrorworks, it allows you to clone and recycle an artifact creature for 3 mana plus the cost of the creature, netting 2 enter/leaves the battlefield effects per cycle.
Sandstone Oracle
It is thoroughly unlikely that someone will have as much card advantage as you. But sometimes your CA will get tied up under a Muse Vessel or in the board in Junk Divers you can't, or don't want to, get rid of. In those cases this can often be a draw 3 or draw 4 on a body that can be recycled like all of the other artifacts and creatures in the deck.
Endbringer
Quite a crazy draw engine in a 4-player game, though he comes with a lot of hate. Also once in a blue moon he will ping someone to death.
Staff of Nin
The best of the tomes. It's like a Phyrexian Arena but it pings them instead of you. Also I seem to remember this costing a bajillion dollars but apparently it doesn't, which I am OK with.