diff --git a/dat/nhlib.lua b/dat/nhlib.lua
index fb35acd1c..983542b5b 100644
--- a/dat/nhlib.lua
+++ b/dat/nhlib.lua
@@ -21,3 +21,23 @@ end
 
 align = { "law", "neutral", "chaos" };
 shuffle(align);
+
+-- d(2,6) = 2d6
+-- d(20) = 1d20 (single argument = implicit 1 die)
+function d(dice, faces)
+   if (faces == nil) then
+      -- 1-arg form: argument "dice" is actually the number of faces
+      return math.random(1, dice)
+   else
+      local sum = 0
+      for i=1,dice do
+         sum = sum + math.random(1, faces)
+      end
+      return sum
+   end
+end
+
+-- percent(20) returns true 20% of the time
+function percent(threshold)
+   return math.random(0,99) < threshold
+end