in chapter 2 there is an "iced over door with a withered sliver of a tree branch encased within".

How do I open it?

Go to the painting at the stairs on level one, one of the topics will change the stairs so that when you go down the stairs, you will end in that room.
To get out, you must kill the golem.
IaaA

I think that the word is Lysara or something like that...

Or it maybe the other one that appears, I can't remeber for sure.

Frosty :eek:
(with memory like a sieve! A SIEVE I TELL YOU!)

You can only do this after you've killed Oria. Return back to the talking painting and choose "In Auril's name bla bla bla" and the stair will lead you inside the room. You cannot get out from the room unless you looted everything inside (i am not sure about this but this is my experience).