From the NannyMUD documentation

LAST CHANGE

2000-12-11

FUNCTION

NAME
        shadow - let the current object shadow another object or find a shadow


SYNTAX
	object shadow(object shadowee, int setshadow)

DESCRIPTION
	If 'setshadow' is 1 set the current object to shadow 'shadowee' if
	'shadowee' hasn't denied shadowing.
	If setshadow is 0 return the object currently shadowing 'shadowee'.