There are two standard tactics to gain a foothold into Howling Stones. The first is to have a character cast invisibility or invisibility to undead on all characters. This will at least reduce your risk to half way. You can then stand at the entrance until all the living beings move far enough away and pray that nothing walks through the entrance way. The first method involved the cleric going in first with divine aura.
Tanks go in immediately after.
This way they can taunt off of the cleric and hopefully stave off the immediate onslaught. The second method also involves going in invisible and invis to undead but it requires a bit more luck. However on the sides of the walkway you will notice a pit that you can fall into. This leads to a room with a gazebo and two more doors out. There is a very small ledge in this room.