I've been playing this deck a lot lately and it mostly worked as designed. It is very reliable and almost never misbehaves. It is always fast, and sometimes is *very* fast. Several times I played decks that had enough counters or board-wipers (e.g.
Whelming Wave) that I had to
rebuild my board, and then I hit a wall because I ran out of cards. Insufficient cards to
rebuild, nothing to discard for counter, and no card draw.
So..... I pulled some lands and added 4
Sign in Blood rather than putting them in the sideboard, because people are cottoning on and doing their best to be serious rat exterminators. It seems to be working, and the loss of life if it happens is fine because of
Crypt Ghast. Common scenarios are that this deck beats people before they're really started or that it does a bunch of damage early, but the opponent keeps the rat tally fairly low and I finish the game with
Crypt Ghast's
extortion.
It's a good deck. I like it.
MuroideaFast, cheap deck. Colony and other rats out;
typhoid rats for blocks if needed;
metallic mimic gets counters on so that the colony or pack rats build up rapidly, don't die from every 1/1, and do a good bit of early damage. Counters, and creature removal help keep the playing field clear or remove the worst threats.
Crypt ghast and
Sign in Blood play the longer game, keeping you in cards and often extorting to finish the game.