If you’ve never encountered a mimic, this pic should tell you all you need to know. These creepy shapeshifters operate by taking the form of a mundane object—treasure chest, dungeon door, half-pony half-monkey monster corpse—and then waiting around for unwary adventurers to blunder by. From there it’s all pointy teeth and grasping tendrils. But even though mimics are famous for becoming anything, they’re not the only critter capable of the trick. I’m not talking about shapeshifters at large though. I’m talking about getting the most out of any monster.

Let me tell you a story to illustrate the point. Last time my group dealt with mimics, it was in Monte Cook’s Dragon’s Delve. The party had found their way down to a mad science themed level, and so the creatures they encountered were were no normal aberrations. They were the story seeds of an entire mimic plague:

Anyone that touches a disease mimic must make a Fort save (DC 15). Failure means that tiny mimic spores enter the victim’s system and begin to grow. Over the course of the next 1d6+4 weeks, the mimic grows, until it gets big enough to begin feasting on the creature from the inside. This has two effects. First, the victim suffers 1 point of Con drain each day until dead. Second, the victim’s appearance begins to warp and twist beyond their control, causing them to suffer 1d3 points of Cha damage per day and giving them the ability to change their shape for 1d6 rounds once per day like a mimic.

What’s interesting here is that Cook was able to take a well-known monster and give it a little twist, changing the mimic enough to make it a different type of threat. He goes on to explain how the victim eventually becomes a mimic, how a remove curse spell can slow the disease, and how a greater dispel magic can cure it. I decided to ignore those bits of text though. Rather than messing with spell cures I had my players go on a quest to collect and then drink wyvern venom. If they could survive the poison the disease would be killed. It was a nice excuse to get them out of town and make the world feel a little bigger. It was also the moment when I realized that GMs are shapeshifters too.

By creating a variant monster Monte Cook expanded on the existing idea of the mimic, creating a more interesting encounter in the process. By ignoring Cook’s built-in solution of “cast some spells to cure the disease,” I was able to generate an entire side quest. My players left town to go wyvern hunting, and I got to design a fun little slot canyon dungeon. For me the lesson was clear: in the same way that game designers like Monte Cook are allowed to expand upon the existing entries in the monster manual, GMs are allowed to alter the ideas in a module, taking ownership of the story and making it their own.

Question of the day then. Have you ever tinkered with the way a monster works, changing it mechanically and making it your own? How did it work out at the table?