Since the damage is not to hit points, bandaging does the trick. I'm assuming the following:
Borimer: 3 pints
Geebo: 2 pints
Fingas: 3 pints
Leo: 2 pints
Tahldar: 3 pints
Kahan: 4 pints
Shae: 3 pints
You are able to measure out the blood in a one pint wood bowl carried by Shae. (I will leave it up to you what healing spells are cast. Cure wounds and cure disease are the two that will help, in addition to bandaging.)
As the last drop pours into the cup, it begins swirling like a tiny whirlpool, draining into a newly formed opening in the bottom which is now glowing a sickly green.
And then the wall beyond parts, opening like a gate of skulls, a door of bones. Given your weakness, you all sit on the ground and simply watch while Kahan administers to you.
What you see beyond is mostly shrouded in darkness and mist, but it glows a deep red. Unlike the chilly hallway, the air beyond the door is hot and burns your nostrils. Flames leap up from little pools of lava spread throughout this cavern. Geysers of hot mud erupt from time to time, releasing a sulfurous stink into the air. Steam rises from the floor of this inferno. A small path, about two feet wide, can be dimly glimpsed through the steam as it winds its way among the lava pools. It leads to a golden door about 90 feet away; the door glistens in the muggy heat.