Dweomersink CR 6
Zones of magical entropy that disrupt spells, dweomersinks are occasionally formed at the sites of great magical duels, by the destruction of powerful artifacts, or by vortices of eldritch energy at the fringes of antimagic zones. They vary in size from small bubbles only a few feet across to large areas the size of a town.
A successful DC 20 Spellcraft check detects a tingling in the air that heralds the presence of a nearby dweomersink. An active spell brought into a dweomersink may be dispelled, and any spell cast inside a dweomersink is subject to an immediate counterspell (both as dispel magic, caster level 8th). The resulting release of magical energy inflicts 1d6 points of damage per spell level in a 5-foot burst centered on the bearer of the spell entering the area or the caster of a new spell (Reflex save DC 15 for half damage). If multiple overlapping bursts hit the same target, only the most damaging applies. Once a spell effect has survived a dispel attempt, it is not affected again unless it leaves and reenters the dweomersink. More powerful dweomersinks are even more disruptive. Each +1 increase in CR increases the caster level of the dispel check by 2 and the save DC for the damaging burst by 1.
Pathfinder RPG GameMastery Guide, © 2010, Paizo Publishing, LLC; Authors: Cam Banks, Wolfgang Baur, Jason Bulmahn, Jim Butler, Eric Cagle, Graeme Davis, Adam Daigle, Joshua J. Frost, James Jacobs, Kenneth Hite, Steven Kenson, Robin Laws, Tito Leati, Rob McCreary, Hal Maclean, Colin McComb, Jason Nelson, David Noonan, Richard Pett, Rich Redman, Sean K Reynolds, F. Wesley Schneider, Amber Scott, Doug Seacat, Mike Selinker, Lisa Stevens, James L. Sutter, Russ Taylor, Penny Williams, Skip Williams, Teeuwynn Woodruff.