This is the one node with a name of its own in game: the Heart of Zjiria, named for Qor’s most trusted lieutenant, and one of the rarest.
Where it is
Ukgoth, Holy Land of Trolls. The marked map is on the location page: Ukgoth, Holy Land of Trolls.
Getting it
The temple floor at Ukgoth stays shut until someone carrying a scepter says Qor the Vile out loud in the room. The floor lifts, the scepter is destroyed, and the way stays open only briefly before it closes again. Bring the scepter with you and say the words standing where you can reach the opening.
Melding
Stand within three squares of the node and use it. The bond raises your maximum mana by three points plus one for every ten points of Mysticism above five, so between three and eight depending on how mystical you are. You can bond with each node once, and the game will list the ones you hold if you ask.