Fountain of Youth Sword
When immersed in a pool of water, that fits certain secret and specific criteria, this sword (along with the gem in its hilt) changes the water into a liquid that impedes aging.
Located at the bottom of a pool just outside the Blue Valley by Rikklind, who was exploring the strange glow in the water. Its gem was one of the ten components of the “potion to restore the kings” (see The Deaths of Trollenkine).
The sword currently resides in a pool of water in the lower levels of Castle LKAB.