Earth Nodes

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.