This rune circle has a deep connection to the Elemental Plane of Earth, and, when creatures are called up from there, this circle allows another creature to come forth.
Aura: Strong Conjuration
Benefit: When a creature within this 20-ft. radius circle uses a summon monster or summon nature's ally spell, the spell summons one extra creature.
If a dwarf or gnome uses the circle, the creatures summoned by the spell all gain the benefit of the Augment Summoning feat for free.
Construction: CL 18th, Craft Rune Circle, Earth Sense, summon monster or summon nature's ally (any level), 50,000 gp.