Throw the spell in there and we're essentially finished.
How's this for the spell, then?:
Summon Fire Phantom
Conjuration (Fire, Summoning)
Level: Brd 3, Clr 3,
Drd 2, Rgr 2, Sor/Wiz 3
Components: V, S, F/DF
Casting Time: 1 round
Range: 30 ft.
Effect: One summoned creature
Duration: 3 rounds/level (D)
Saving Throw: None
Spell Resistance: No
This spell summons a fire phantom. It appears where you designate and acts immediately, on your turn. It attacks your opponents to the best of its ability. If you can communicate with the creature, you can direct it not to attack, to attack particular enemies, or to perform other actions. The phantom must always remain within 30’ of the spellcaster; if it moves beyond this range the spell expires.
Fire phantoms are subservient toward more powerful fire elementals. A fire elemental can easily dismiss a summoned fire phantom back to the elemental plane of fire.
A summoned monster cannot summon or otherwise conjure another creature, nor can it use any teleportation or planar travel abilities. Creatures cannot be summoned into an environment that cannot support them.
Arcane Focus: A pint of oil which must be poured out and ignited during the casting of the spell.
I'm tempted to expand the flavor a bit just to jazz 'em up. Maybe they're not fully-formed fire elementals, or the form on the fringes of the Elemental Plane of Fire's borders where the elements are diluted? Something to explain their "phantom" moniker. In the description, perhaps they don't burn as brightly as normal flames, or are somewhat translucent?
Maybe their flames include strange, ghostly colours (green-blue?). I quite like the somewhat translucent bit, too.
A vaguely humanoid figure formed out of fire. The bulk of its flames are green-blue and translucent, but hot streaks of red or orange occasionally burn through its body.
As for the "phantom" moniker, I'd rather leave it undecided, but don't mind fleshing out some "sages theories", e.g.:
There are conflicting explanations as to why they are called fire phantoms. It may be because their eldritch green-blue colour matches the natural atmospheric phenomena known as "ghostlights" or "corpse candles". Some scholars believe they are called phantoms because they're not fully formed fire elementals, having been born in areas of the elemental plane of fire where the fire energies are weak and diluted. A few sages theorize they are masses of elemental fire that have absorbed the psychic "impressions" or "residue" of fire elementals and thus animated. The latter theory would explain their subservience to the will of true fire elementals.