Stone is a condition in which a character is turned into stone (or petrified), being unable to move.
In Fire Emblem: The Sacred Stones, it is caused by Gorgons that carry Stone on them. It contains 5 charges and has the range of a longbow (the target cannot retaliate back). If it hits, the target will be turned to stone for 5 turns, which can be fixed with Latona or a restore staff. While petrified, attackers have a 100% hit rate in addition to an increased critical hit rate on them. If the target is hit with another stone again, the duration resets again. Stone can also be used to teach any unit dark magic with the control enemy glitch, though it will leave the character with a magic stat and not strength stat.
In Fire Emblem: Radiant Dawn, Nailah's Glare ability can turn enemies to stone until the end of the level or until they are killed. However, the unit suffering from this condition also gets a bonus 10 defense.