Dynamic Shield

Rathgar pulled the strange shield from the slain serpent man's arm.  The colors of it's face were shifting from blue to yellow-green in a very fluid motion.

"Are you sure you want to be taking that?"  Nimble asked.  "You don't know where it's been."

"It's unusual, but I don't think it's evil."  Allianora chimed in.

"It may be cursed." Feris added helpfully. 

"Well, I need a shield." Rathgar stated.  "My last one got eaten by that owlbear."

Nimble looked skeptical.

"Tell you what.  Until we can get a good look at the thing, I'll use one of these wooden ones.  And if it does end up being cursed I'll just hang it over the mantle.  Does that sound fair to everyone?"

The Dynamic Shield is a round metal shield enchanted with protective magics.  The face of the shield shows a constantly changing flow of colors.  It usually is a somewhat slow movement, but during combat, especially combat involving spells and other magical effects, the surface is in a constant state of agitation.  In addition this visual show, the Dynamic Shield serves as a magical shield +2, that also provides a +4 to the last type of saving throw it's owner had to make.

For example, if Rathgar had to make a saving throw versus spells last round, he would get a +4 to his saving throw vs spells until he has to make a different saving throw.  If he then has to make a saving throw vs Dragons Breath, he'll get no bonus this round, but from next round on the bonus will shift to Dragons Breath.