[SixOfSpades]

Non-Detection will shield a character in Stealth (NOT Invisibility) against such spells as Detect Illusions--instead of revealing the character, the Divination spell will only cancel out the Non-Detection spell. This does not really protect against the spells of True Sight and True Seeing, however, since because the first "wave" of the spell cancels your Non-Detection, the second wave will make you visible. Therefore, only ITEMS that confer permanent Non-Detection are of any real use.

However, all of this is a rather moot point in this forum, because NONE of the spellcasters in BG1 use any type of Divination spells anyway (unless, perhaps, when using BGT or BGtutu), so the Cloak is completely and utterly worthless in BG1.