A Lifestone is used to help heal people. It is consumed in the lum spell which can be used to heal light wounds in yourself and others.

Elanore will make 5 lifestones in exchange ten each of all the following: gamboge leaves , alizarin leaves, mauve leaves, and cobalt leaves.

You can create a lifestone with the spell lifestone-enchant Which Elanore will teach you when you are sufficiently powerful.