|On a field invisible, an invisible man proper,|
dressed in mail of the first
Unlike a ring or cloak, however, the shield only hides its user from those creatures which are viewing it from basically the front, in an arc of 60°, 120°, or 180° for the largest versions. Likewise, the small version only hides figures of elf or smaller stature, the medium size hides those of less than ogre size, and the large any being of hill giant or less height.
In combat, the shield allows a full +5 to AC (one for the shield and 4 for being invisible) when opponents are unaware of the user's whereabouts. After one round's worth of attacks by the user, the bonus drops to +3 as their opponent can see flashes of movement as the weapon arm makes its attacks (seeming to appear from thin air) and the shield itself is moved about in combat. Since these bonuses are not magical pluses in the normal sense, they can stack with any other magical defences.
The shield's invisibility bonus of +4 applies to saving throws against specifically targeted spells such as disintegrate, but against area effect spells or breath weapons it has no effect on saving throws. Against magic missile, the shield grants a saving throw (at +4). If the roll succeeds then then caster has pointed in the wrong direction and either struck some other living thing (see firing into melee discussion on DMG p63
Naturally, these bonuses only apply to opponents who are not attacking/viewing from an area the shield covers.
The normal chance to detect invisible creatures (DMG p60) apply even when the user is not attacking, but simply using the shield for stealth, although this does not in itself modify any of the shield's combat or saving throw bonuses.
Xp: 500/650/800 by size.
Gp: 2500/3000/4000 by size.