I recently talked a lot about why flying foes can cause problems for low-level PCs, and it reminded me about a related topic from one of the first published adventures I wrote. There’s a monster in 3rd edition D&D called an ethereal marauder. It lives in the Ethereal Plane, from which it can see into the regular world but can’t be spotted or attacked except by certain specific, high-level magic. It darts in from the Ethereal Plane, attacks, and retreats there all in the space of a single combat round. And its Challenge Rating is 3. Even novice adventurers might face one.

Now, I get a sense of how this monster is supposed to be fought. It’s a lesson in readying attacks, striking when the opportunity arises, sticking together to limit its ability to munch on isolated PCs, and so on. From a design perspective, it’s a “teaching” monster. But that always bothered me, because an ethereal marauder isn’t stupid. It knows enough to just wait for the right moment, watching from a position it can’t be seen or attacked, then attack and fade away while the PCs are readjusting or are less prepared. Scary, but not very fun for its victims.

That seemed to invite a challenge. So I wrote a low-level adventure around a smart, old, powerful ethereal marauder. It was terrorizing some NPCs who, though skilled, didn’t have any way to fight this type of foe. The PCs didn’t have a way to fight it, either—they were low level—so they had to undertake a short quest to get some magic that would lock the ethereal marauder in their world long enough to defeat it. PCs that went off on their own got attacked, and to drive this point home, some NPCs that went off on their own got attacked where the PCs could find out about it (and learn that doing so might not be smart!).

The monster’s ability to attack the PCs freely was something that could be used to pick them all off in a non-fun ambush-y way. Instead, I built an adventure around bringing the foe into a toe-to-toe fight with the PC. That led to a much more satisfying confrontation. Whether a monster can fly, swim, or shift through the planes to avoid being attacked, put some thought into how the PCs can face it in a dramatic way. Your PCs will certainly want to do so!