Air Elemental

An air elemental on the party's side is almost always a summon. A druid's Conjure Elemental, a genie's gift, a binding circle in an Auran-marked tower the party just inherited. Establish the leash up front: how many rounds, what command words work, what happens when concentration drops. The fun of an ally elemental is that it's powerful and stupid, so the players have to point it at the right target before it scrambles their own formation.

In combat, run it as a brutal opener and then as area denial. Whirlwind on the densest cluster of enemies, then position in a doorway or chokepoint where its hover and Air Form let it phase through gaps the party's heavy armor can't fit. Resistance to physical damage and immunity to poison and thunder mean it tanks for several rounds without much help. Don't bother coordinating with the party's spellcaster; the elemental does not understand the plan, only the last instruction.

When the duration ends or the binding lapses, the elemental returns to the Plane of Air without ceremony. Don't let the players treat it like a recurring NPC. Auran isn't even guaranteed at the table, and a Charisma of 6 means it has nothing interesting to say if they could parse it.

If a player asks the elemental to scout, give them a moment of static, a rush of cold air, and an impression of a wide room and many warm bodies. Don't roleplay paragraphs from a thing with Intelligence 6.

An air elemental is a moving hazard with attacks attached. Walking speed is 10 ft. but it hovers at 90 ft. of fly, which means terrain doesn't exist for this fight. Use that. Fight on a windswept ledge, in a temple atrium, over a chasm, anywhere the party can't simply line up and trade hits. The elemental should be coming from above or behind cover the party can't reach.

Lead with Whirlwind if the recharge is up. DC 13 Strength save against 4d10+2 thunder, plus a 20-foot push and Prone, and the target started inside the elemental's space because Air Form lets it move in there for free. The right opener is to drift through the wizard's square, save against Whirlwind, then continue to a position the rest of the party can't easily reach. If Whirlwind is spent, fall back to two Thunderous Slam attacks at +8 for 2d8+5 thunder each. Reach 10 ft. plus hover means it's striking from a corner of its space the party can't get into without the climb.

Target priority is whoever has the lowest Strength save. Whirlwind only hits Medium or smaller creatures, so the elemental will phase through ranks of fighters to find the bard. Resistance to bludgeoning, piercing, and slashing means basic weapon attacks chip slowly, while immunity to grappled, prone, restrained, and unconscious shuts down most of the party's lockdown options. Players will look for the trick. There isn't one. They have to out-damage 90 HP under resistance.

The elemental doesn't panic and doesn't bargain. It was bound or unleashed for a purpose, and it carries out that purpose until destroyed or until the binding ends. If you want a cleaner exit, tie the elemental to an object the party can break, a sigil scratched into stone, a bound scroll a cultist is holding. Knock that out and the elemental dissolves mid-turn.