Whether from supernatural influence or simply from more mundane physical forces, windows can sometimes explode in a rain of glass shards.
When this occurs, for each 5-foot square containing an exploding window, the shattered glass blasts out in a 15-foot cone that deals 1d6 points of slashing damage to each creature in the area (Reflex DC 12 negates). A creature caught in more than one of these cones (either from multiple simultaneous exploding windows or one large exploding window) takes a cumulative –1 penalty on its saving throw for each cone beyond the first, but attempts only a single saving throw and takes only 1d6 points of damage if it fails, regardless of the number of cones whose areas overlap on the creature’s space. Additionally, the glass shards remain on the ground, functioning as caltrops until they are cleared away.
Pathfinder Roleplaying Game Horror Adventures © 2016, Paizo Inc.; Authors: John Bennett, Clinton J. Boomer, Logan Bonner, Robert Brookes, Jason Bulmahn, Ross Byers, Jim Groves, Steven Helt, Thurston Hillman, Eric Hindley, Brandon Hodge, Mikko Kallio, Jason Nelson, Tom Phillips, Stephen Radney-MacFarland, Alistair Rigg, Alex Riggs, David N. Ross, F. Wesley Schneider, David Schwartz, Mark Seifter, and Linda Zayas-Palmer.