If Hackmaster hadn't already beaten us to the name, I'd go with Grunge Elves.
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Not quite happy with it yet, but here goes nothing.
Naphtha Nereid
You see a humanoid like being composed of blue fire. It is androgynous but has both incredibly striking eyes and a multicolored flame where it’s hair would be that comes to a point.
Knowledge. Parapsychology, Arcana (Common DC 12, Unusual DC 14, Secret DC 16).
Common knowledge. These spirits are made of natural gas and are found through the Scooped Valley of Alberta, but often migrate throughout Strathcan.
Unusual knowledge. They are believed to be the reincarnation of a oil and gas industry mascot that has been given life from the Hodgepocalypse.
Secret Knowledge. If a Naphtha Nereid agrees to do something, they will do it or die trying, regardless of whether they want to do it. They do get resentful if it is beyond their abilities though and are not into hyperbole. They do like keeping people they like warm and safe and often enter agreements with the locals to deal with the cold Canadian winters.
Naphtha Nereid
Small Elemental, Lawful Neutral
Armor Class 16 (natural armor)
Hit Points 45 (10d8)
Speed 30 ft.; Fly30 ft. (hover)
STR DEX CON INT WIS CHA
10 (+0) 14 (+2) 10 (+0) 12 (+1) 13 (+1) 17 (+3)
Saving Throws: Int +5, Wis +5, Cha +7
Skills: Arcana +6, Deception +5, Perception +4, Sense Motive +5, Stealth +5
Damage Immunities: Fire
Senses: Darkvision 120 ft., Natural illumination 120 ft., passive Perception 14
Languages: Hallowed Speech, Trade Tongue and one of choice.
Challenge: 8 (3,900 XP) Prof. +3
Elemental Demise. If the Naphtha Nereid dies, its body disintegrates in a flash of fire and puff of smoke, leaving behind only equipment the monster was wearing or carrying. Furthermore, all those within 20 feet radius must make a Dexterity save dc, or suffer 3d6 fire damage (save for half).
Innate Spellcasting. The Naphtha Nereid's innate spell casting ability is Charisma (spell save DC 14, +6 to hit with spell attacks). It can innately cast the following Spells, requiring no material components:
At will: Produce Flame,
3/day: Expeditious Retreat, Tongues
1/day each: Gaseous Form, Wall of Fire
Transparency. When in an area filled with fire, a Naphtha Nereid’s body becomes transparent, effectively rendering her invisible. She can become visible or transparent on her turn without using an action.
Actions
Multiattack. The Naphtha Nereid makes two melee attacks or uses a hurl flame twice.
Hurl Flame. Ranged Weapon Attack: +5 to hit, range 120 ft., one creature/target. Hit: 14 (4d6) fire Damage.
Flame Blade. Melee Weapon Attack: +3 to hit, reach 5 ft., one target. Hit: 6 (3d6) fire damage. Can create or make disappear as a bonus action.