Soul Anchor

Soul Anchors were initially referenced as the particular item that trapped Thordak in the Elemental Plane of Fire. However, since then, that same item has been referred to as a Heartstone.

My current understanding is that a Soul Anchor is any constructed object that serves the purpose of locking a being's soul to a particular plane of existence (likely against the being's will). A Heartstone may be used as a Soul Anchor, but it also may be used for other things, and things other than Heartstone may be Soul Anchors.

Raishan also referred to the thing in Thordak as a "Binding Stone", which seems more synonymous with Soul Anchor based on how it was used. Raishan also references "corrupting" the Binding Stone, which supports the idea
This is only the current understanding though, and might need updating later.

Item type

Magical