The Commons
I find that Cultists can be quite useful even without being mutated. They are great for finishing off units at range, while staying towards the back of the board. Remember that every common you lose that wasn't mutated denies you an extra mutation that you could have summoned. No commons, no mutations.
Because Zealots are only melee attackers, they are much harder to use safely when not mutated. I also find their negative ability, Bloodlust, surprisingly restrictive. All in all, when I want to summon a common and immediately mutate it, a Zealot is what I use. However, Shield of the Hopeful works well with Zealots, as it gives you a blocker or an extra attacker than you can protect from being killed.
Anointed come in the Filth's re-enforcement pack and they are the only Filth common that doesn't cost zero to play. I have yet to use any Anointed, as I find they are a bit expensive in a deck that has so many summoning options at all times. On the other hand, a ranged unit that can heal off a wound every turn might be powerful. I can see Shield of the Hopeful being very powerful with the Anointed. Use it to save them from being killed off before they can heal.
Champions
What a fun champion! The abomination is all about the extreme. A high cost of 8 magic, for 7 life, and anywhere from 1-6 attack per turn. Try not to rely on getting a high attack value roll every turn, as it is unlikely. The Abomination is also sure to get focused on by your opponent. Use this to your advantage by placing Abomination where he can lure out enemy units. This should also give your other more fragile units more freedom to more and attack without getting focused down. Also if you only have the base deck this is the only champion for the Filth that you will have available.
Her is the first of two champions that come in the Filth re-enforcement pack. Her is a very powerful champion that is frequently seen in Filth decks. The strategy here is simple, summon her in the back and sit tight while you ping off the enemy commons or finish off champions every turn. At 6 magic and only 3 life, you need to protect her for a couple of turns to be able to get value out of her. It is much easier to gain back the magic used to summon her against an enemy with a large amount of 1 life units.
I don't typically run Vomitus in my Filth decks, as I find Abom and Her more fun. At only 5 cost, he is a cheaper option in a champion spot then the other two, and he works well with the typical Filth strategy of sitting back and attacking from afar. Like with Her, you are going to want to summon Vomitus in the back of your board and pop out to get line of sight for a long range attack. However, Vomitus can handle direct combat much better than Her can, since he sports 2 attack and 5 life.
Well that covers all the commons and champions available for the Filth, part 3 will cover all the Mutation units that are unique to the Filth Faction. Check out the previous faction breakdown on the Sand Goblins and be sure to leave a comment.