Some cards were put into the Sideboard instead and aren't mentioned below. A noticeable one is Cover of Darkness as it was only needed if I came across sky blockers. Here are the main cuts.

• Lightning Greaves - this was the toughest choice. It's just not thematic enough to be included in a deck based on dreams/sleep/nightmares. Might have to include something in the future or see if it's even needed. Maybe something like Whispersilk Cloak but if other folks have protection/haste options, let me know.
• House Guildmage - another tough choice. He was GREAT early game but did almost nothing the rest of the game and felt like a wasted slot mid-to-late game.
• Sakashima the Impostor - mana heavy and less effective than Cryptoplasm. I have enough copy spells for cheaper with more flexibility. I also found a substitution that is more akin to Lazav (see the "In" section below).
• Strionic Resonator - if I had access to more ramp, this card would be a great addition. But more often times than not, I found it more beneficial to cast a spell instead of paying for it's cost.
• Royal Assassin - great card but highly situational and also ineffective mid-to-late game.
• Sleep with the Fishes - too gimmicky and not effective enough.
• Worst Fears - too mana heavy and not effective enough.
• Chromatic Lantern - would be better if I had another land instead.
• Dimir House Guard - not thematic enough and I found a better tutor for cheaper.
• Thespian's Stage - too gimmicky. I'd often just use it for the colorless mana instead. Mirage Mirror was more effective and flexible to play instead.
• Diabolic Tutor and Rhystic Tutor - found better alternatives and I had enough tutors already.

Now for the fun part.

• Thief of Sanity - Used to be in the first conception of this deck but now put back. One of this deck's strengths is using my opponent's board against them and this gives me more options.
• Everdream - thematic and able to be used constantly due to it's splice cost. Happy to take more draw.
• Brainstorm and Aphotic Wisps - more draw options with flexibility. AW also gives me target choices and helps me get a creature in if need be.
• Maddening Imp - this card is insane. If all of my opponent's creatures are tapped and can't attack, it means they're all destroyed. I now have an effective boardwipe!
• Siren's Call - Great backup to the above.
• Orvar, the All-Form - I always have the chance to tap my opponent's creatures. But I also have the high likelihood of tapping my own! I like the idea of my creatures falling asleep only to have them awake to a mirror image of themselves. And with cipher spells like Hidden Strings, this card is non-brainer. Surprised it took me so long to have it included.
• Likeness Looter - I've always wanted a Faerie to add to the deck as they are highly associated with Dreams. Likeness looter is the replacement for Sakashima the Impostor and acts as a secondary Lazav, the Multifarious but with Flying! It also gets me draw and discard options. Ridiculous card for only 2 CMC!
• Demonic Tutor - Always wanted this card in a deck. Finally got the chance to add one and it's the artwork I wanted too. It's like a Demon being told a bed-time story. XD
• Shadowmage Infiltrator - I knew I was going to add this card eventually. Found out about the alt art and imagine it was another form of Mr. Sandman.
• Cryptic Command - Gives me Sleep + Draw + other options all in one and I can choose from 2. Yes please.
• Dreamshackle Geist - speaks for itself.
• Misleading Signpost - Hilarious card and great mana rock. Say Maddening Imp or Siren's Call comes to bite me, I can change the direction of my opponent's attack to another opponent. Having a confusing signpost suddenly pop up feels very dreamlike.
• Skyline Cascade & Mystic Sanctuary - the first works as Fogwalker and gives me another land to work with. The second counts as an Island and also gives me the chance to get another of my spells back - including Demonic Tutor.