The seeker's charm is a special necklace dropped by seekers in Daemonheim. It provides a damage bonus for all three combat types. The necklace looks like the seeker's eye. It is only dropped by the seeker, which requires 71 Slayer to kill.
It is one of the only two items worn in the necklace slot dropped inside the dungeons of Daemonheim, the other being the blood necklace.