Holylight

From SBIWiki

Holylight is an Immortal command that makes the user able to see everything (except for higher invis Immortals), such as dark rooms, hidden players and so on.

[edit] Helpfile

Syntax: holylight
Syntax: invis

HOLYLIGHT is a toggle that allows you to see (almost) every character and
mobile in the game.  With holy light, you can see what's in the game more
easily.  Without holy light, you can see what mortal players see.

INVIS is a toggle which makes you completely invisible to all player characters
of lower level than you, and to all mobiles.

When an immortal is INVIS, they will have a flag on the who list which 
indicates their level of invisibility, such as (51) for INVIS 51.  A 
similar flag will also appear when you 'LOOK' in a room - this flag will 
say (Invis 51).

HOLYLIGHT will not allow you to see immortal INVIS characters who are
higher level than you.

This article is incomplete and needs more information in order to be of better use.