Replace shade encyclopedia entry.

Sourced from xnethack. Seems like an excellent candidate for
replacement, since the quote gets across what shades are and also
hints at their weakness.

dat/data.base

@@ -4824,10 +4824,27 @@ seth
 	hippopotamus, and the pig.
 		[ Encyclopedia Mythica, ed. M.F. Lindemans ]
 shad*
-	Shades are undead creatures.  They differ from zombies in
-	that a zombie is an undead animation of a corpse, while a
-	shade is an undead creature magically created by the use
-	of black magic.
+	For the shades -- figures of jet black streaking acrossthe
+	white-knobbed ground -- were upon her. Strength was meaningless
+	against shades. They had no real substance. Only two things
+	mattered: moving quickly and not letting yourself be
+	frightened. Shades were dangerous, but so long as you had silver,
+	you could fight. [...]
+
+	Her knife passed through the shade with a slight tugging feeling,
+	creating a shower of bright white sparks that sprayed out of the
+	shade. The shade pulled back, its black tendrils writhing about
+	one another.
+
+	Silence spun on the other. The pitch sky let her see only the
+	thing's eyes, a horrid green, as it reached for her. She lunged.
+
+	Its spectral hands were upon her, the icy cold of its fingers
+	gripping her arm below the elbow. She could feel it. Shade fingers
+	had substance; they could grab you, hold you back. Only silver
+	warded them away. Only with silver could you fight.
+		[ Shadows for Silence in the Forests of Hell,
+		  by Brandon Sanderson ]
 shaman karnov
 	Making his quarters in the Caves of the Ancestors, Shaman
 	Karnov unceasingly tries to shield his neanderthal people