When you start your turn at Night, play two 1/1 Rats that can't block.
At the end of your turn, if you have three or more Rats, sacrifice Argenport Sewers.
Summon - Does something when played
Nightfall - The first Nightfall card played in a turn makes it Night and extends it by a turn for each player.
Night - When you start a turn at Night, draw an additional card and take 1 damage.