Hello everyone! Here is a small walktrough of the game!
1/ Exit the crypt, and go to the small tent outside nearby.
2/ Once arrived at Lubana, go to the INN, speak with the lady.
3/ Go to the townhall.
4/ Go back at the INN. Go upstars then to the empty bedroom.
5/ Leave Lubana, and go to the Merchants Guild (Manor at the south of the lake).
6/ After the cinematic with the staff, go to the left upstairs and enter the first bedroom.
7/ Return to the staff member, then go to the door behind him.
8/ Downstairs go in the corridor and upstairs to reach the meeting chamber.
9/ Go outside, then to the forest. North-East from the guild.
10/ As Vik and Alexander said, one map to the north and one to the east.
11/ Enter the lake, take the Fire Stone and defeat the boss.
Congrats! You went through the full story!