thehod wrote: It says you have to place a webway portal as long as it is in base contact with the model deploying it and is considered impassable. What happens if you move the model to such a way you then can place it on an enemy model? Does it count for being destroyed or is the placement illegal?
It wouldn't technically be illegal, as far as I can see... but the rules don't cover what would happen. I would go with not placing it over other models to avoid problems, personally.
One thing is models in impassable terrain are destroyed.
Sorry, but there is no such rule.
Models can not generally move into Impassable terrain, but there is no rule that says that a model that finds itself somehow in Impassable terrain is destroyed.
One other question is is the bearer considered destroyed if he is in base contact with impassable terrain?
No. See above.