I simply adore this theme! I just built a sanity focused deck my self but not to this extent!
Hollowborn Barghest isn't a rat, but the ability is quite good with your game plan.
Hi there, i'll share all the knowledge i've gathered after playing discard decks for more than 5 years (i've built monoblack creatureless discard, monoblack creature discard, UB discard, RB discard, Grixis discard, specter discard, etc.).
The first i see here is that you don't have anything to deal with the board, so you'll more than probably die to anything that hits the board, even a simple 3/1 two-drop. Your deck relies too much on damaging your opponent through giving him many cards and forcing him to discard not that many; the only card in your deck that punishes him this way is Liliana's Caress and that's it, it's not reliable. You also run two copies of Painful Quandary which it's ideal mechanics are to punish your opponent for having no hand, but since you are forcing him to draw so many cards, he'll always have the option to discard while playing a spell (only taking 2 damage from Liliana's Caress and only if you have the enchant on the battlefield).
You have many cards that allow you or your opponent to draw and discard cards, but you only have Alms of the Vein to exploit this mechanic, so get rid of those or stick in more madness cards.
The description says "the goal of this deck is to get your opponent as low as possible", but you can't do that quickly by relying only on 4 copies of Liliana's Caress while you'll be recieving lot's of threats and hits. Master of the Feast will for sure get destroyed by any of the thousands removal spells you'll force your opponent to draw, so it won't be dealing too much damage if any.
Let's work on the solution. First of all, you need your deck to have more consistant way to deal damage and you also need to get rid of your opponent's threats until you've reached mid-late game and you can develop your winning mechanics.
Since you have almost no creature, let's take advantage of that so that you can trade one card of yours for many cards of your opponent. Good cards to do this, depending on the money you want to spend are, for example, Drown in Sorrow , Yahenni's Expertise , Languish and Damnation.
You also need to be faster or at least to be able to delay your opponent's strategy. A way of doing this is by disrupting his early moves to wreck his plan. Cards like Inquisition of Kozilek , Thoughtseize , Duress and Despise excell at doing so.
To strenghten the draw and discard engine you have many cards at your disposal. I don't know if you want to keep the deck in the modern format or to build a casual free of legal restriction deck, so I'll recommend a variety of cards like Chains of Mephistopheles , Probe , Wheel and Deal , Ill-Gotten Gains , Urza's Guilt , Anvil of Bogardan , Whispering Madness , Dark Deal , Font of Mythos , Forced Fruition , Geier Reach Sanitarium , Memory Jar and Temple Bell.
You need more cards than Liliana's Caress to punish your opponent for discarding or drawing cards. All of these are good for the task, suit yourself: Underworld Dreams , Psychosis Crawler , Fate Unraveler , Waste Not , Megrim and Words of Waste.
Since you and your opponent will be drawing lots of cards, you will be able to discard cards too or abuse your card-drawing. This does not only work well for madness, but also with delve, retrace and other cards. Consider some of these: Chain of Smog , Last Rites , Big Game Hunter , Raven's Crime , Syphon Life , Cunning Lethemancer , Necrogen Mists , Psychotic Haze , Call to the Netherworld , Dark Withering , Gibbering Descent and also Sphinx's Tutelage.
You'll be forcing your opponent to draw many many cards, so you'll need cards that make him discard more than one to win the trade. Consistant massive discard cards are for example this ones: Brink of Madness , Mindstab , Mind Twist , Mind Shatter or Delirium Skeins.
Pick the ones you like the most according to their mana costs and their price. Also consider the ammount of black mana symbols in their cost, because you'll be playing a two colors deck.
Try to keep it as balanced as you can in terms of cards functions. Maybe 30% draw/discard engine - 30% draw/discard punishment - 20% massive discard - 10% 1drops quality discard - 10% board whipe. You'll have to test and adjust the numbers.
I know most of those cards are black, but you can keep it UB if you want to. Best version I've made of this strategy was using Grixis (Blue Black and Red) because there's a lot of red cards that force both players to discard and draw like Burning Inquiry and Reforge the Soul for example. Grixis also enables the use of Nekusar, the Mindrazer , Blightning , Sedraxis Specter , Blazing Specter and Dack Fayden.
I hope it's helpful! Best wishes!
Hi there! I worked on a very similar build before the Commander 2017 Series, and I have a few tips.
ADD: Vampire Nocturnus, Bloodline Keeper Flip, Captivating Vampire, Olivia Voldaren, Purphoros, God of the Forge, Smuggler's Copter, Lightning Bolt, Mogis, God of Slaughter, Living Death, Kalitas, Traitor of Ghet, Coat of Arms, Phyrexian Arena, Outpost Siege, Living Death.
Rabid_Wombat of course there are other.
Hitting Eternal Dominion and Decree of Annihilation is probably win since You are picking value of opponents libraries while everyone else have nothing.
Soul Conduit + Treasonous Ogre mean You can pay almost your whole life and switch it with someone elses.
Scrambleverse/Thieves' Auction + Brand often makes everyone else scoop.
Warp World + Gather Specimens is also crazy good and often end games.
Other simple cards that win games late are Insurrection and Disrupt Decorum.
This deck doesn't really aim straight to win, more just to make fun games. You can also win with long painful games making everyone into topdeck mode while killing everyone slowly with Creeping Dread and Gibbering Descent.