Streams of invisible power run beneath the earth, occasionally crossing and collecting in a single spot like a river flowing into a lake. Such rare collection points are called earth nodes. These nodes are usually anywhere from 30 feet across to a half mile wide.
Effect: An earth node focuses magic, allowing the following uses:
A node can be used as if it were a permanent teleportation circle. If it is used as a destination, those using it arrive at the center of the node.
While in the node, an arcane caster can make a DC 25 Arcana check as a standard action. On a successful check, that caster gains a +1 bonus to any one d20 roll it makes each round and a +1 bonus to damage rolls with arcane attack powers. These bonuses last until the caster leaves the node.
An earth node can have rituals tied to it. The most common rituals are: Linked Portal, Planar Portal, and Leomund’s Secret Chest. Even creatures without the Ritual Caster feat can access these rituals, as long as those creatures are the appropriate level.
Usage: An earth node can make an interesting encounter location in addition to being a type of terrain. Usually found underground, nodes are often guarded by powerful magical creatures. Intelligent creatures like drow will take advantage of the +1 bonus, if able. An earth node is a good way to create an encounter where waves of opponents enter the combat at different intervals using the node’s teleportation effect.
Published in Forgotten Realms Campaign Guide, page(s) 51.