Despite every caver insisting on a good supply of torches and candles, they all end up feeling the ground in the dark while cursing \gls{yonder} eventually.
Those who know their environment have a knack for crawling efficiently, feeling the surroundings through their fingertips and beards, and remembering every passage they took in the light simply through the sounds of their own breathing echoing uniquely in every cavern-segment.
\index{Black Walking}
\index{Caving!Black Walking}
\subsubsection{\Glsfmttext{gagingCave}}
\glsdesc{gagingCave}
\index{Caving!Detecting sloping passages}
Despite gradual gradients, or sharp ups and downs, a good caver knows exactly how far they sit from the surface at all times.
\subsubsection{\Glsfmttext{echoing}}
\glsdesc{echoing}
Rolling a tie might indicate knowing that one has descended or ascended, but with no idea how much.
Understanding what altitude one has reached immediately indicates whether there might be running water, what type of rocks and minerals compose the surroundings (and therefore the chance of a cave-in), and how far one has to go to the surface.
Nobody survives long underground unless they can tell if the ceiling might collapse from heavy footfall.
\index{Caving!Note weak tunnel}
\index{Caving!Echoing}
\makeRule{echoing}{Echoing}{Wits}{Caving}{10 to find the general size of a cavern, 16 to find which tunnel opens up later}
With a little practice, people can gauge the size of a dark cavern above by giving a loud whistle and listening for the return.
And with real expertise, they can find out if a tunnel opens up later on.
More advanced cavers know a variety of different whistles, and use them almost like a discussion with the \gls{deep}.
Nobody admits they have misjudged a tunnel -- they prefer to say `the \gls{deep} lied to me'.
\makeRule{hypoxia}{Hypoxia}{Intelligence}{Caving}{10 to notice problem, gain \glsfmtlongpl{ep} on failure}
\index{Hypoxia}
\index{Caving!Hypoxia}
\noindent
Long, underground tunnels don't have a lot of oxygen.
Taking a torch down one, or even staying down too long, and sucking up all the oxygen, can cause hypoxia.
Once hypoxia begins, people will feel light headed, confused, and dizzy.
If any \gls{pc} succeeds in the roll, they understand that hypoxia has settled in, and can put out their torches in order to stop the penalty increasing too quickly, and will probably try to move elsewhere.
If the \glspl{pc} fail the roll, the \gls{gm} should increase the \gls{tn} for all rolls, without explaining why the \gls{tn} for most actions have risen, and continue increasing the \gls{tn} until the party find themselves weak, and confused, or manage to get out the other side.
Once out, all penalties vanish, except for a single \gls{ep}.
\makeRule{place_fire}{Placing Fire Underground}{Intelligence}{Caving}{11 to avoid filling the cavern with smoke, and receiving 1~\glsfmttext{ep} each round}
A fire in the wrong place underground can easily choke everyone around to death, or at least until they can't think properly.
Of course, this provides an excellent weapon of war if one can do it properly.
Light the wrong type of fire, and heavy smoke will fall down a tunnel instead of rising.
\index{Caving!Placing Fire}
Failure indicates nearby characters suffer 2~\glspl{ep}, and everyone in the area suffers \pgls{ep} each round after that.
\subsubsection{\Glsfmtplural{caveFire}}
\glsdesc{caveFire}
\makeRule{run_in_dark}{Running in the Dark}{Wits}{Caving}{12}
\index{Caving!Running in the dark}%
A bright torch adds a +3 Bonus.
A tie means the character comes to a sudden halt, without Damage.
Failure means $1D6$ Damage, plus the character's Speed (running faster means more Damage).
\index{Darkness!Running}
\index{Caving!Walking}
\makeRule{walk_underground}{Walking Underground}{Dexterity}{Caving}{8, plus 2 per mile}
Caverns offer all manner of impediments, from sudden drops to falling debris, and passages full of water.
Each mile covered inflicts 2~\glspl{ep} -- double the usual.
Each \gls{interval}, the \glspl{pc} decide how many miles they wish to cover, and make a roll.
Proper equipment, such as ropes, good shoes, and a map, can add up to a +3 Bonus.
\caveTravelChart
Failure results in an additional 3~\glspl{ep}, as the characters bang their head, twist an ankle, or bruise their arse on slippery fall.
A tie means they can see the danger coming, and choose to rest instead of taking the \glspl{ep}, then carrying on with a plan for the route.
