diff --git a/commands.tex b/commands.tex
index 5efec7d0e57e53fdcb7044c356d6c76b3ead5868..7496c171f028fd2ef66a260c940f3f96084997ed 100644
--- a/commands.tex
+++ b/commands.tex
@@ -271,3 +271,21 @@
     < 4 & < 3 & Slowburn ivy: gain 2 \glspl{fatigue} each interval until you find a cure (Intelligence + Medicine, \tn[8]). \\
   \end{nametable}
 }
+
+\newcommand\caveTravelChart{
+  \sidebox{
+    \begin{boxtable}[YYY]
+
+      \textbf{Miles} & \textbf{\glsentrytext{tn}} & \textbf{\Glsfmtplural{fatigue}} \\\hline
+
+      0  & 10 & 0/ 3 \\
+
+      1  & 12 & 2/ 5 \\
+
+      2  & 14 & 4/ 7 \\
+
+      3  & 16 & 6/ 9 \\
+
+    \end{boxtable}
+  }%
+}
diff --git a/systems.tex b/systems.tex
index 66b755b5214a349ab64063dd9bebd15e9c0d477e..444567970e87f135b513003ae500ab0d4017176b 100644
--- a/systems.tex
+++ b/systems.tex
@@ -117,6 +117,16 @@ If the \glspl{pc} fail the roll, the \gls{gm} should increase the \gls{tn} for a
 
 Once out, all penalties vanish, except for a single \gls{fatigue}.
 
+\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.
+
+\index{Spelunking!Walking}
+\caveTravelChart
+
+Each \gls{interval}, the \glspl{pc} decide how many miles they wish to cover, and make a roll.
+Proper equipment, such as ropes, a harness, and a map, can add up to +3.
+Failure results in an additional 3~\glspl{fatigue}, as the characters bang their head, twist an ankle, or bruise their arse on slippery fall.
+
 \subsection{Town Activities}
 
 \makeRule{marching}{Judging services}{Wits}{Empathy}{9}