Relentless Rats EDH uses your general Maralen to tutor for the set pieces you need. Thrumming stone is the key piece of your deck that must be tutored for. After you play Thrumming stone, play a single Relentless Rat, and now your entire deck of 50 Relentless Rats will spill out onto the battlefield.
Step 1: Play Maralen
Step 2: Maralen tutors for Thrumming Stone
Step 3: Maralen tutors For Cull The Weak. Use Cull the Weak to sacrifice Maralen for the mana to play Thrumming Stone
Step 4: Play one Relentless Rat
Step 5: Pass Turn and hope no one boardwipes
Step 6: Unleash the Rat Horde!
....
Step 7 Profit???
Pros: Relentless Rats EDH
Killing ALL of your opponents with Relentless Rats.
Cons: This deck is a one-trick pony, and thus has serious flaws if any one of your set pieces gets eliminated. If someone counterspells a single piece, the whole deck falls apart. If you do manage to drop Thrumming Stone>>Relentless Rats, you have to hope that they don't boardwipe, especially exiling. If they do boardwipe and your Rats go to the graveyard, then graveyard removal like Bojuka Bog and Relic of Progenitus will knock you out of the game.
There are a few cards that will help you out like Kozilek and Exilir of Immortality that will shuffle your Rats back into your library. Cull the Weak actually helps you out by eliminating your Maralen tutor which everyone has access to for the first one to two rounds. If your opponents boardwipe, then you can play Living Death to turn the tables. Temporal Extortion usually will cause someone to lose half their life, but if you do get that extra turn, you can swing for the win.
Any suggestions on how to speed up the deck would be appreciated =)