your deck description is spot on

may I suggest Nightmare Lash and Lashwrithe ?

THANK YOU GEOXIS!

you are so vry welcome sire

Good! But it isn't a real mnoblack discard, because there are some different "combo". So, I suggest:

1) planeswalker: if you want to play Liliana of the Dark Realms , you have to take advantage of his great mana ability, so add 2x Lashwrithe , not in sideboard. You can add also Consume Spirit or Mind Sludge (but i don't like discard spell that cost so much). But if you want a real discard deck you have to play Liliana Vess or Liliana of the Veil

2) creatures: with Liliana of the Dark Realms you have to take creatures with trample, because take advantage of his second ability: Phyrexian Negator , Phyrexian Obliterator (i know, are expensive card) or you can take 3x Ogre Marauder ! Is a good combo, to kill a creature and pump it with Liliana! There's also Tormented Soul , is too little, but if you equip it with Lashwrithe ...

Instead, for a discard deck Hypnotic Specter is the best, but you have to take also other good creatures like this: Stabwhisker the Odious (i like it very much!), Abyssal Nocturnus , Guul Draz Specter .

Knight of Infamy is a sideboard card in this deck; Royal Assassin only 1x, because he deals no damage and it's fragile. Skirsdag High Priest is not good for this deck, i think

If you want to see a very fast discard deck, take a look at my The BIG DISCARD!