Potent Portals (2003)

From the introduction:

Portals are everywhere. They can be found in nearly every castle, wizard’s tower, temple, monastery, or mansion. The mundane ones are meant to restrict access and offer a modest means of security against the uncertain outside world. What if those portals were enhanced with magic? Their usefulness increases exponentially. Some are intended to be cruel traps to keep out intruders; others are meant as defensive mechanisms. Regardless of their intent, magical portals provide a new alternative in protecting one’s property.

Potent Portals offers some clever new tools for DMs and players alike to enhance a building’s defensives or to add to its mystic. Imagine your players’ reaction when they go speak to a local baron and the amusing pompous door extols for several minutes his "wondrous virtues." Or the cry of horror from the rogue as his favorite pick was broken in two by a snaplock. Some of the portals detailed in the following pages are ones you’ve probably used in your own game, but likely without the game mechanics detailed behind it. Creative Mountain Games does this work for you.

What’s truly wonderful about this product is its scalability. The portals vary in power from the simple flare lock providing a challenge to low level characters up to the fatal death’s door striking fear into the hearts of the most veteran RPG players.