Sub in shadowheart and use her pass without trace ability. The but your party into stealth mode with c, that should hopefully leet you maneuver a bit.
There is a smoke powder barrel in the back right corner of the room, throw it on ragzlin's followers.
If you strait up need another enterence there is a spot you can snowfall too on the other side of the river, then walk across a land bridge, there is a crumbling wall you can destroy to get in
