The FAQ says:

Q: When a hero switches spaces with the Shadow Soul familiar, can the Overlord play a Trap - Space card on said hero?
A: Yes.

Just to get sure: What is the interaction between Shadowcloak and other "special spaces". What happens, if a hero swapping places will enter...

1) ...a space containing ice. Does he have to roll for the surge? (I would say yes) The same question (and the same answer) to trap spaces and lava.

2) ...a space adjacant to a monster with aura. Does he get the damage? (I would say yes)

3) ...a space containing a pit. Does he get the damage from falling into the pit? (I would say no because the shadow soul familiar has already been on the ground of the pit. But in this special case, you could say that the hero is entering the space and is ergo falling into the pit.)

The FAQ ruling suggests that a hero swapping places with Shadow Soul counts as "entering the space" where Shadow Soul previously was. As such, I would say "yes" to all of the points you bring up. The logic of Shadow Soul already being at the bottom of an existing pit sounds good in theory, but Descent is not always a logical game and as far as illogical rulings go, this one doesn't even make the top ten.

If swapping with SS does count as entering a space, then we must treat swapping on top of an existing pit as if the hero has just entered the pit space. That means (s)he takes damage and falls. Ruling otherwise would require us to further define which situations will count as "entering a space" when swapping with Shadow Soul and which situations don't, which is a bit more fiddly than I care to get with the rules.

Edit: I suppose you could take the following stand: A hero who enters a pit space from a non-pit space takes damage and falls, but a hero who enters one pit space from another does not. (This is established RAW.) Thus, if the hero is already in a pit somewhere on the map and swaps with Shadow Soul, who is in another pit, then no damage will be dealt. If the hero is not in a pit already, they will. I can't remember if the RAW explicitly states the "no damage" rule is from *adjacent* pit spaces or if it merely assumes they must be adjacent if the hero is moving from one to another.

My brain is leaking out my ears now, so I think I'd just go with "yes the hero always takes damage" to keep things simple.

Thank you for your quick response. I agree with your explanations.