Not every creature in the Monster Manual exists to kill your party. Some exist to question them, to whisper truths they’d rather ignore. And few do that better than a rainbow-colored serpent that has the power to alter destiny.

The Couatl – a winged, rainbow-feathered celestial – is an impressive creature in the D&D Multiverse, usually working in service of a higher power. Now, at CR 4, it’s not all that threatening on paper, unless you have a low-level party of murderhobos who think they can make a pretty penny selling Couatl feathers. Which they could, sure, if they survive the encounter and the aftermath of having killed a divine being. It can bite and constrict, and it has some spells available to it, but even a cursory look will tell you that this is not a TPK monster. Ideally, it’s not even a monster that your party should be fighting at all.

At its wingtips are powerful and useful spells such as Dream, Detect Magic, Greater and Lesser Restoration, and Scrying. These are creatures of healing and knowledge, and have an awareness of the world that your players will likely lack. The Couatl is a guardian not just of treasure, but of knowledge, and if there is any role that this creature should play in your campaign, that’s it.

Your players might need access to a divine secret, something only the beings of celestial scope can know. A Couatl may be guarding that knowledge, ready to put them to the test to see if they are worthy of it. Pass, and they may learn things no other mortal knows. Fail, and there might be a surprise visit from an Empyrean to deal with their audacity. Even if they should pass, and gain the secret knowledge that they need, the Couatl may ask them to swear a powerful oath – one that makes their overall journey much more difficult.

A Couatl may also be a way to test their morality, something not every table is really ready for. Perhaps they are asked to escort a Couatl egg across planes while fiends and zealots chase them. And maybe – just maybe – that egg has the power to heal. Or is valuable enough to bring hope to a village or a town close to your players. You can give your party a choice where none of the options feel comfortable, but where a creature that is removed from the mortal world in the way a Couatl is may not see the problem.

If your party is making a difficult journey, either physically or figuratively, a Couatl may be an excellent guide. They know the secret paths and the hidden ways, but they may have a strange sense of what “the proper way” might be. In a moral journey, the Couatl may end up having a very alien idea of what “justice” is, and force your players to decide if they really want to resolve a conflict in a way that makes a detached, celestial being happy. Maybe the death of a beloved NPC is key to restoring some kind of cosmic imbalance. Can your players do what is asked of them, or will mortal justice have to prevail?

Your players aren’t going to meet a Couatl in a tavern (probably – these beings can cast Shape Change at will, so if you want your friendly local tavern keeper to be a disguised celestial, you absolutely can), but they may meet one in their dreams. Night after night, a call to action, to come, to listen, to help, until the only option to actually get any rest at night is to seek out this voice that haunts them.

Creatures like Couatls can also be great for those of us who came to being Dungeon Masters via having been theater kids. You can play your Couatl as inscrutable being, speaking in riddles and allusions, never actually lying to the players, but never telling them the whole truth. Your Couatl isn’t really interested in mortal problems and issues. They’re interested in maintaining cosmic order and making sure that evil is kept at bay.

In this way, you can use a Couatl to open up your game to higher orders of moral truths. Most of the time, the moral truth of a D&D campaign is wound up around very normal, moral motives: there is a thing that is dangerous to life, and that thing must be destroyed. But to a celestial – an immortal servant of cosmic good – what do individual mortal lives matter? With a being who can see the future and adjudicate the balance of cosmic order, how do you convince it that the lives of shopkeepers and tavern owners and farmers, and maybe even adventurers have merit?

A creature like this can add that mythic element to your game, and show your players that the stakes of their adventure matter far beyond the streets of their city or the bounds of a kingdom. Their actions are being observed by entities that consider themselves “good,” but in a way that may be unrecognizable to the short-lived mortal types. They want a goodness that is not easy, or even recognizable.

The Couatl doesn’t care what your players want. It cares about what’s right. At least, as it sees it. So when your party finally stands before this rainbow-winged oracle, the question isn’t whether they’ll survive. It’s whether they’ll agree on what “good” truly means.