This deck appears to be a black-green creature-based control-combo deck that aims to generate card advantage and board presence.
    The creature suite seems to be focused around cheap efficient creatures with abilities to generate a lot of value like Chained Throatseeker and Phyrexian Digester.
    One suggestion could be to work on color balance, you can add some more black or green sources to make sure that the deck has enough colored mana to cast spells consistently.
    Another suggestion could be to include more ways to generate card advantage or removal spells, a lot of card advantage in this deck comes from only Chained Throatseeker, which could be susceptible to removal, adding more card advantage and removal spells will make it less vulnerable to disruption.
    Another suggestion would be to include a few sideboard cards, which can be added or swapped depending on the matchup and the meta.
    Finally, this is a small and unique sample of cards and not a complete deck, in order to complete the deck, it may require to add more cards and make cuts as per the need.

Please note that this is just a sample deck and the suggestions made could be changed according to the meta, playstyle or personal preferences.

Creatures:
- 4x Skithiryx, the Blight Dragon
- 4x Phyrexian Crusader
- 4x Plague Stinger
- 4x Contagion Clasp
- 4x Contagion Engine

Instants and Sorceries:
- 4x Contagion
- 4x Putrefy
- 4x In Garruk's Wake

Enchantments:
- 4x Contagion Bog
- 4x Contagion Spreader
- 4x Contagion Epidemic

Artifacts:
- 4x Grafted Exoskeleton
- 4x Nihil Spellbomb

Lands:
- 4x Dimir Guildgate
- 4x Dismal Backwater
- 4x Forest
- 4x Island
- 4x Jungle Hollow
- 4x Swamp
- 4x Thornwood Falls