I really can't find any infos about this..

Shadow Souls have no defense and no life and can be placed on any terrain and under any figure..

Can monsters attack it/can it suffer damage from any effects/area effects?

And if so, what happens?

Can they be "dispelled"/removed by the OL somehow?

EDIT:

Okay, we found that it can not be attacked or targeted by stuff and is immune by stuff that only goes for heroes/figures, as it isn't one..

BUT: Are there any effects that can affect it? Like conditions, area effects/damage, any other way to get rid of it?

Or are they completely immune and free to roam over the map as they wish?

A space containing a shadow soul is an empty space. It just happens to be an empty space containing a shadow soul (like an empty space can contain a search token.)

Shadow souls cannot suffer damage for any reason. They do not have a health value, so this would be meaningless anyway.

They cannot be forced to take attribute tests.

Essentially, the only way to interact with a shadow soul at all (this goes for pico and skye, too) is via the abilities of the hero controlling him. That is, if it's not on a shadow walker class card, the shadow soul can't be made to do it.

The shadow soul can activate, but it can only do a move action by itself, and its speed is 1. It treats all terrain as water, which means that it can't enter any special terrain (since its speed is only 1.)

The OL cannot forcibly dispell it, though he can drain the shadow walker of fatigue or kill her so that she can't use her abilities.

Okay, thanks very much

Seems they're pretty simple

Can the Shadow Walker dispell the Shadow Soul by casting a new one?

Can the Shadow Walker dispell the Shadow Soul by casting a new one?

The abilities that can place the shadow soul such as Soul Bound and Faithful Friend can be done regardless of whether the soul was already on the map or not.

So, yes, it can be repositioned using these sorts of abilities.