A jinni (the fifth-edition Monster Manual uses the variant spelling “djinni”) is the product of a humanoid soul bound to the elemental essence of air. By default, jinn are chaotic good, but they’re also haughty and vengeful, and a party of players may find themselves fighting one if it’s trying to get payback against someone who once betrayed it. Jinn don’t reproduce naturally, so they don’t have the same kind of evolved behaviors as creatures that reproduce over generations have, but they are keen to preserve their own existence—not to mention slick hagglers—and will readily parley with anyone they recognize as a major threat.
Jinn have high Dexterity and extraordinarily high Strength and Constitution, an ability contour that suggests a brute fighter but really allows them to fight however they want. They also have high Intelligence and Wisdom and extraordinarily high Charisma, giving them a strong self-preservation impulse, shrewd target selection, the ability to strategize and, most of all, the ability and willingness to seek negotiated solutions to conflict. Their saving throws and damage immunities don’t have much bearing on their fighting style, except insofar as they aren’t afraid of most spellcasters. You’ve got to be at the top of your game to beat a jinni that way.
The jinni’s triple scimitar Multiattack, which does not only slashing damage but also bonus lightning or thunder damage, is a simple but severe damage dealer: against armor class 15, each attack has a 75 percent chance to hit, for expected damage of 12 hp per attack and 35 hp for all three. Create Whirlwind is useful for restraining enemies, upping the chance to hit to 93.75 percent and the total expected damage to 44 hp.
Most jinni spells aren’t oriented toward combat (it’s a rare creature that will use create food and water to hurl smoked hams), but a few are. Conjure elemental can summon an ally whose tactics we’ve looked at already. Gaseous form, invisibility and plane shift offer paths of escape, and plane shift can also be used offensively against a single foe. Major image can create a distraction. That notorious nothingburger thunderwave becomes genuinely useful to a jinni surrounded by melee attackers, thanks to its spell save DC of 17 and the fact that it can cast it at will.
A jinni will take you seriously if you can inflict a moderate injury on it (reduce it to 112 hp or fewer) or if, somehow, you can preemptively demonstrate your ability to do so. A party of four adventurers who can each reliably deal 12 hp of damage or more per turn—I’m talking probabilistically, meaning that on average, each player character will deal 12 hp or more, taking into account chance to hit against AC 17 and normal distribution of damage die rolls—can probably convey this information by their bearing and conduct alone, as can a party of five who can deal 10 hp or more apiece or a party of six who can deal 8 hp or more apiece.
And if a jinn takes the PCs seriously, it will parley with them, seeking a bargain that serves both its own interests and the PCs’. This is assuming, however, that the PCs don’t insult it. If they do, it will seek a bargain that serves its own interests and seems to serve the PCs’ interests as well but actually screws them over. Jinn may be chaotic good by alignment, but they take insolence from no one. The creation spell is a good way for a jinni to swindle rude PCs, since the products it “creates”—which can include gold and gems—fall to dust after 10 minutes to an hour. Or it might summon the PCs an elemental “servant” that turns on them once the jinni is safely on its way.
If a fight is unavoidable, a jinni will use Create Whirlwind, its most distinctive feature, immediately at the outset of combat. Depending on the makeup of the opposition, it might Create Whirlwind to capture a cluster of opponents, to restrain its most powerful melee opponent or to take a potentially bothersome ranged attacker out of play. The jinni then moves the whirlwind around to scoop up multiple opponents until it can’t contain any more. Its capacity is substantial: covering four 5-foot squares (or three 5-foot hexes) and 30 feet in height, it can hold three or four Medium-size enemies in each of three “stories.” The jinni can also fly, holding itself up out of reach of melee attackers while it’s doing this.
Next, the jinni Multiattacks with its scimitar against the most powerful opponent within reach, especially one already restrained by the jinni’s whirlwind. If at any time the jinni is being flanked by melee opponents (see “Optional Rule: Flanking,” Dungeon Master’s Guide, page 251—I always use this rule), it casts thunderwave to repel them, then flies around to a position where it can face all its enemies. (Its AC is high enough that it could probably just fly to a new position, then Multiattack, without paying much heed to opportunity attacks, but casting thunderwave is like a Disengage action that does free damage at the same time.) A spellcaster who’s powerful enough to lob a spell past the jinni’s defenses and do at least 49 hp of damage to it, and who botches his or her DC 17 Charisma saving throw, will suddenly find himself or herself plane shifted to the Elemental Plane of Air.
If talk has failed and so has fighting, a jinni bugs out when seriously injured (reduced to 64 hp or fewer), using gaseous form or plane shift.