These cards are the heart of the deck. You begin by casting one of the loot spells to either dig for more dredgers, dredge existing dredgers, or dump dredgers from your hand. When starting your first turn, it's more beneficial to start with a
Faithless Looting to start the engine then follow up with either
Cathartic Reunion or
Insolent Neonate to keep going.
Golgari Grave-Troll: The keystone of the deck. It's the biggest dredger. Hardcasting it may be one option to start finishing your opponent.
Stinkweed Imp: MVP when dealing with creatures and flyers. This creature has 'pseudodeathtouch', allowing you to kill a creature it dealt combat damage to. Second best dredger in the deck, so don't feel bad for not seeing a Grave-Troll.
Faithless Looting: Allows you to a) dig for cards, b) dredge two times for 1 mana, c) dump dredgers into the grave, and d) provide excellent late game dredges with flashback.
Insolent Neonate: Considered an instant-speed mini Tormenting Voice. For 1 mana, you get a 1/1 with menace that can provide early damage that can equal to a Lightning Bolt and then can be sacrificed to discard a dredger or payoff card and start dredging. Another use for this creature is as an early chump blocker that can block for you then activate, absorbing all that damage in the process.
Tormenting Voice / Cathartic Reunion: Tormenting Voice used to look like a backwards Faithless Looting that, if countered, still got dredgers in the grave on turn 2. However, Kaladesh provided us with some much needed love in the form of Cathartic Reunion, which allows us (still for ) to dump 2 cards (mainly dredgers) to dredge 3 times by turn 2. If we assume you chain 3 Grave-Trolls, that's 18 cards. If you count one Grave-Troll at Draw Phase, that's 24 cards, allowing you to see more than 1/2 of your entire library by turn 2, which probably goes over anything can do on the same clock.