This is a T2 deck I brought to Standards, and while very resilient, fell
to faster more aggro decks - and perhaps too finicky to work - but when it
works, it works REAL good.

At times, I was considering milling myself (putting Glimpse in, for myself) to junktroll my deck to what I like (full deck tutor) - other times I'm thinking I should throw in blue for some protection against disruption. All the transmutes are 1-mana cheaper Diabolic Tutors. I believe the weakest link is Darkblast, but I don't mind dredging away stuff to return to the bottom of the library. With the Puzzlebox/Troller, it gets to the top rather quickly.

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Puzzled Dreams (Mono Black Combo/Control?)

3 Dark blast ( bop and other annoying first turn plays)
3 Disembowel

4 Last Gasp
4 Shred Memory (for Transmute, over Cremate)
1 Reito Lantern (non-Troller, multi card return for mid-late game)

4 Dimir Machination (Transmute, more than out of game)
4 Underworld Dreams
1 Rend Flesh (Transmuted for..)

4 Teferi's Puzzlebox
4 Dimir Houseguard (Transmute, or fear beats - likely transmute)
4 Junktroller
2 Hideous Laughter

22 Dimir Aqueduct (in case I play the Glimpse/Evac -otherwise just accel)
20 Swamp

Side:
1 Glimpse of the Unthinkable (just to get ahead on cards should the combo
not finish them off)
2 Evacuation
3 Rend Flesh
2 Rend Spirit
2 Hideous Laughter
2 Dimir Aqueducts
3 Pithing Needle
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Best against slow decks, handful of cards = much hurts each turn - with a minimum of 2 (1 dreams, one box). Most opponents tend to try dumping their hands quick (recklessly?) to avoid dmg and go for the quick kill. This is a lose/lose situation for them. If they hold cards, they get better card rotation, but hurt more. They spend cards, they don't get rotation (essentially only drawing every 2nd card), while I hold on to as many as I can to find more dmg pieces or transmute for it.

It shines against dredge/grave combos, cos I respond and remove the dredge
cards to the bottom of his/her lib.

Suggestions?

-Elfy

Looks like a pretty solid deck idea, Elfy.  Underworld Dreams decks are always fun, and you've really used the Transmute mechanic to good effect here.  The only trouble I see is that your Transmute cards Shred Memory and Dimir Machinations don't really seem to do enough on their own.  It's not really a problem if you're just using them for Transmuting, but four copies of Shred Memory in a deck with 4 Junktroller and a Reito Lantern is just too many cards dedicated to graveyard destruction.  So for the first revision, take out Shred Memory.  I know, it's a Transmute spell, but all it's Transmuting for here is Last Gasp and Reito Lantern.  Transmute decks do well to focus on one or two converted mana costs, and this one isn't tutoring up your key combo pieces, so it can go.  In its place, bring the three Rend Flesh from the sideboard into the maindeck.  That'll give the Dimir Machinations some more pull in the deck, and give you some more answers for aggresive creature-heavy decks.  Though actually, Rend Flesh migh be better off as Seal of Doom-- while Rend Flesh and the Seal have different restrictions on what they can hit, once Teferi's Puzzle Box hits the board, you can't hold on to Rend Flesh and wait for the right time, you'll have to Transmute for Rend Flesh or wait to draw it again.  The Seal you can play now, and have it sit on the board waiting for a creature to pose a threat.  Although, if you play a lot of Black decks, the Seal might not be effective at all, so leaving the Rend Flesh in could easily be the wiser move.  Either way, that fourth slot we can fill in later.
 

More importantly, I think you're missing a serious area of potential.  Underworld Dreams is strongest in a deck that can make its opponent draw a lot of cards.  Teferi's Puzzle Box is obviously your main way of making that happen, but there's room for more I'd say.  That fourth slot I just mentioned?  Make it a Mikokoro, Center of the Sea.  The extra draw will help you, as well as do a point of damage to the opponent and keep their hand size up for more Puzzle Box pain.  And those three slots in you sideboard should become either Vision Skeins or Skyscribing, for similar reasons.
 

That ought to solve most, if not all, of your problems.  I had also hoped to add in a low-cost creature to help you against aggressive decks, but you do have 16 creature removal spells, so you shouldn't need it.  But if you do, the creature I was going to suggest was Lurking Informant.  It's not a great card, but it comes down quick, you don't usually mind chump blocking with it, and in a deck that encourages its opponents to draw a lot of cards, it never hurts to have a look at what they're going to draw and possibly deny them of it.
 

One last parting thought: I don't care how many Junktrollers you have, don't play Glimpse the Unthinkable on yourself.  In 99% of cases, it's not worth the effort, and as yousaid, the Puzzle Box helps Junktrolled cards rise to the top quickly.