Like Largent said, concising your deck to 60 cards is vital. That is because every deck has a strategy and needs consistency in drawing essential cards.
Looking at your list I think the deck is suffering from indecisiveness - does it want to be a LD (land destruction) deck, Void, Sui or something else?
Regardless of strategy, the weakest cards in your list are the following because they are either inefficient on their own or do not suit the strategy:
1 x Demonic Hordes
4 x Mole Worms
2 x Worms of the Earth
2 x Word Of Command
4 x Rhystic Tutor
2 x Death Grip
2 x Gloom
2 x Terror
2 x Underworld Dreams
4 x Drain Life
To me the rest of your deck looks much like a Nether Void deck, which is a course I recommend if you like mana denial. I recommend you read Zherbus' primer (
part 1,
part 2,
part 3) to better understand how the deck works and which cards to use and why.
Here's the first decklist from the primer:
Devil's Bile, by Zherbus
Creatures (12)
4 Nantuko Shades
4 Hypnotic Specters
4 Mishra's Factory
Disruption (15)
4 Sinkhole
4 Hymn to Tourach
4 Duress
3 Nether Void
Removal (3)
3 Powder Kegs
Broken (4)
1 Demonic Tutor
1 Yawgmoths Will
1 Demonic Consultation
1 Necropotence
Mana (26) (30 w/Mishra's)
4 Dark Rituals
1 Strip Mine
4 Wasteland
1 Sol Ring
1 Black Lotus
1 Mox Jet
14 Swamps
Obviously if you stay casual and do not aim for competitiveness, you may make adjustments according to personal preference.
Another route in which you can take your deck is a Megrim based deck with heavy discard. Such a deck could look something like this (I used to play this casually):
Dark Dreams.decSpells (35)
4 Duress
4 Hymn To Tourach
4 Night's Whisper
3 Innocent Blood
3 Megrim
3 Chains of Mephistopheles
3 Underworld Dreams
4 Anvil Of Bogardan
2 Ensnaring Bridge
1 Memory Jar
1 Mind Twist
1 Necropotence
1 Yawgmoth's Will
1 Demonic Tutor
Manasources (25)
14 Swamp
4 Dark Ritual
4 Wasteland
1 Strip Mine
1 Lotus Petal
1 Sol Ring
Hope I gave you some ideas as to how to improve your deck. You should also look into Sui Black as an option if you want to take an aggressive route with disruption and a tendency to hurt oneself.