Up, where the fire spirit is stronger. Ok.
The keeper of fire, despite fierce opposition from some men of the party, soon managed to sway the most religious warriors. Thus the party, with the keeper at the lead, took the leftmost passage and soon started ascending.
The path was steep indeed, the smooth, featureless walls leading on and on, with no side branches, nothing to indicate they were moving at all except the increasing fatigue.
After an arduous, hour-long trek, one of the hunters furrowed his brow: 'It's getting warmer in here. Perhaps we are drawing near to an exit? Yet I do not smell fresh air.'
They kept walking, the keeper of fire spurring them ever forward. The heat increased, until everyone was freely sweating. A strange, bubbling noise came from the front, first faint, then increasingly louder.
Suddenly the tunnel widened and a huge cave was in front of their eyes. It was more than big enough to contain base camp, but that was not its dominating feature. The torches weren't necessary anymore, the walls and ceiling of the cave were bathed in an ominous red, flickering light...
In the center of the cave there was a pool of liquid, as wide as three men laying head to feet. It was in constant motion, bubbles opening up and releasing their content towards the ceiling. High up, a small hole let a beam of daylight in. The beam fell straight at the center of the pool, where a small pillar of shiny, black obsidian rose to the height of a man's waist. The heat was almost unbearable.
On the smooth surface of the pillar, a great red stone, its surface faceted. From within the stone, red light came, pulsing, at times barely visible, then suddenly almost blinding.
As soon as the party entered the cave, all the torches suddenly roared, projecting their flames high in the air. Some of them were surprised by the phenomenon and tossed the branches of the grounds. Others grimly held on, others yet fell on their knees praying to the fire spirit.
Everyone reacted. Everyone, but the keeper of fire. He stood still, unmoving, his eyes unblinkingly fixed to the gem at the center of the pool. He murmured: 'The fire spirit... it is strong here. Much stronger than I ever felt it... it is calling to me... - and suddenly started walking towards the pillar.
The head of the militia frowned and started walking next to him, trying to speak to him, but to no avail. The closer they got to the pool of red liquid, the stronger the heat grew, until it started hurting.
The head to the militia grabbed the keeper of fire, trying to stop him.
A. He turned to his men and shouted:
'Help me! He lost control of himself! This heat comes from the red liquid, it is deadly! He is going to die if we don't stop him!'
B. A few militiamen started moving, but others stood in front of them:
'Let him go! The fire spirit has called him, who are we to stop an holy man?'
C. The scouts and the hunters started to walk back to the entrance tunnel:
'We don't like this. Leave him to his fate, we should run out of here, never turning back!'