Hey,
first of all, interesting idea playing with Damia as commander for a rat deck.
I've got some questions/suggestions for you.
First of all, the mana base:
Why are you plaing
Farseek? Don't get me wrong, i like that card, but i see no reason to play it while you just have basic lands. I would replace it with
Sakura Tribe Elder (he also fetches you a basic land and works as early blocker) or add lands like
Sunken Hollow or dualshocks (
Breeding Pool etc).
The same goes for
Voyaging Satyr. Thats a creature I would only play if i can get more than 1 mana out of a land (which is kinda difficult for you). Unless you got Crypt Gast out,
Urborg Elf would be a much better option.
Even on a Budget like now you could cut a
Island and
Forest and add
Tainted Isle and Tainted
Forest in stead. With your amount of swamps it shouldn't be a problem to get 1 of them out.
Then i would add the full set of Lockets/Cluestones, or replace them with Signets for some additional mana ramp.
About your creatures:
Are you sure about
Trinket Mage and
Trophy Mage? you only got 1 Target for Trinket and 2 for Trophy. Even if the Targets are nice to have, they dont seem to be essential enough to add tutors for that special targets.
Then, what about
Ratcatcher? Yes, hes expensive mana wise, but he fetches you a
rat colony every turn.
Marrow-Gnawer could be another interesting addition for your deck. With your amount of Rats on the battlefield, you could
flood the board even more. Besides that, the
Rat Colony also scales with rat tokens.
About your spells:
In stead of Muder you could play
Curtains' Call. With 3 opponents it has the same effective cmc than
murder, but you can kill 2 creatures in stead of one.
Naturalize and
Krosan Grip could be very interesting in case you need more Enchantment/Artifact hate.
If you want to make your Rats even stronger,
Coat of Arms would be a very interesting option. With 10 Rat Colonies on the battlefield, the coat would boost them up to 20/10.
What about an discard outlet, to generate more value with Damia?
Dreamscape Artist and
Silverglade Pathfinder could be interesting options, since they help you ramping and thin your deck out.