Lands: Basic Swamps all the way. They enter untapped and activate Defile which is particularly effective against Atog, blockers and other impactful creatures. Barren Moor enters tapped, but you will always want to cycle if you already have five or six lands.
Creatures:Sewer Rats is an aggressive one drop that you can sink spare mana into for extra damage.
Typhoid Rats is a one mana investment that trades with anything on the battlefield. It often goes unblocked and it blocks well itself.
Ravenous Rats and Burglar Rat are the best two drops to play on turn two. They provide imediate value and allow your Rat Colony to hit the board with high power.
Alternatively, Rat Colony on turn two can attack on turn three for significantly more damage, but will be an early target for removal. 10 copies of this card provide a barrage of high power attackers throughout the game.
Chittering Rats is a walking Time Walk. The 2/2 body protects againt electrickery and trades with more creatures and deals more damage than the Ravenous boys. The card to the top of library is similar to discarding, but prevents the opponent from digging for more recources and answers instead of depleting their current recouces.
Spells: Dark Ritual provides high impact turns and explosive starts. It allows you to play a draw spell on curve without missing a creature play on curve.
Defile is a powerhouse removal spell for one mana that averts indestructability, nullifies Atog-Fling if cast just before a lethal number of artifacts have been sacrificed, and scales well into the late game.
Night's Whisper and Sign in Blood allow the deck to push threats in the late game, find fuel in grindy matchups, mitigate mulligans and dig for answers and side board pieces. Sign in Blood can also burn the opponent to finish a game.
Side Board: Crypt Rats is our go to board wipe. It can swing as a creature and boost our rat count for Colony, but more importantly can clear the way for a coming storm of rats, save us from a dire board state, or fireball the opponent to finish a game.
Duress stops all the shenanigans that the rest of the deck cannot. It answers threats, disruption and resources preemptively for only one mana but is far less impactful when drawn in the late game.
Relic of Progenitus stops flicker combos, Pulse of Murasa, delve and flackback.
Okiba-Gang Shinobi bounces your discard rats for enormous value against control, often putting them into topdeck mode and closing out the game.
Oubliette is your catch-all removal for three mana.
Unexpected Fangs wins aggro mirrors. It flashes in, shifting the tides of combat, provides lifegain and increases your beatdown.
Maybe Board: A sideboard of 15x Relentless Rats is very difficult to answer in pauper. It can make the deck more aggressive and resilient by siding out some number of chittering rats, burglar rat, ravenous rats, rat colony, night's whisper, and sign in blood. Alternative side board.
Dash Hopes can function as a counterspell against disruption with the drawback of offering the opponent a reasonable alternative. In this deck, a burn spell that deals 5 damage to an opponent for two mana is also a considerable card due to the speed of the deck. Possible main board inclusion.
Peat Bog provides burst mana which this decks can make use of, particularly on turns two through five where you want to provide a lot of pressure on the board. Unfortunately it enters tapped, preventing the on curve plays that make the deck so fast. It also sacrifices itself after two uses, making the deck less sustainable in long matches.
Gray Merchant of Asphodel averts fog, providing a finisher in certain matchups. It also has a large body, surviving board wipes and trading and attacking well. The primary reason to include this is for burst damage to close out a game or lifegain to outlast other aggressive decks. Unfortunately it is not a RAT, so we will not play it :]
