Hey, he posts another card!
I take it protects stacks, not each component individually
I don't really understand that, so I'll try and use an example
Assume you played an air tower, air pend, unstable gas, shard of gratitude, EE, and fog shield in that order. That'd be 6 permanents. With 3 airborne creatures on the field your tower, pend, and UG would be protected. With 4 creatures, your fog shield would be included as well. With 5, SoG, and with 6, EE would be protected. There's no real advantage to having multiple Stolas besides more protection and safety. As long as one Stolas exists on your side of the field with its ability, the field protection will take effect.