Oh Thallid, you so awesome! Thallid is great because it's the creature that keeps on giving. It also works amazing when put in the right deck. Sporoloth Ancient makes this little guy go off in 2 turns rather than 1, almost doubling his capacity to make gribblies. Sporesower Thallid also speeds him up (with the Ancient, he works every turn). Finally, Doubling Season was made for this card (not really, but you know what I mean). With all three cards, he makes 4 1/1 gribblies every turn! The only drawback to him is that he's just a soldier on his lonesome and needs something to speed him up to make it worthwhile. A 1/1 every 3 turns is nice, but 4 1/1s every turn is better.
Pros: Reliable gribblie-maker
Cons: Needs back-up to work at full potential