Just finished playing Flies and Spiders, and found that Eagles of the Misty Mountains behaves interestingly in this scenario.
Eagles of the Misty Mountains reads:
"Eagles of the Misty Mountains cannot have restricted attachments. Eagles of the Misty Mountains gets +1 and +1for each facedown attachment it has."
The On the Doorstep rules insert says the following about poison:
"Facedown cards attached to chararcters are considered "poison." Poison cards are Condition attachments, and characters with any number of poison attached are considered 'poisoned.'"
There's a little conflict here, since the Venom mechanic and the Eagles of the Misty Mountains card both use facedown cards as attachments. I guess there are three possible ways to resolve:
1) Keep the Eagles' "eagle" attachments separated from the "poison" attachments.
2) All facedown attachments are considered poison; ignore the Eagle's text.
3) All facedown attachments are considered poison, but because they are still facedown attachments, they will simultaneously poison and power up Eagles of the Misty Mountains.
How would you play this? I chose to read the rules as literally as I felt was possible, and went with #3. This made the Eagles card interesting -- it can quickly be powered up by allowing it to be poisoned, but triggering his Response and attaching more Eagles to them will also increase their poison… so they can be rendered unconcious very quickly, also.