Ok all incorporated - only quibble I have really is that its fire aura now does more fire damage than its firefist and musing whether this seems a bit counterintuitive
Damn it, I forgot about the
Fire Aura.
That'd add 70 fire damage to the DPR, since it's a 10d6 AoE, which'll increase the CR considerable.
How about we change the
Smoke Cloud so it doesn't do damage but causes some other effect (blindness and choking perhaps?) and use the 2d10 damage for the
Fire Form? Then the DPR portion of the Challenge Rating will remain the same.
Also, as you said it'd seem odd if the Aura's fire damage exceeds that of its flaming fist. A regular Fire Elemental's Fire Form does 1d10 damage after all, which is considerably less than the 2d6+3 fire of its Touch attack.
Furthermore, it seems weird to give it both Fire Aura AND Fire Form, since there's so much overlap in their effect.
Hmm… the Fire Aura is basically the "radiant heat" portion of Fire Form, so how about we use a new Special Trait for the "conductive heat" portion (i.e. the elemental doing fire damage to creatures that touch it) and combine that with its fluidic flame body?
Something like this:
Fire Aura. At the start of the fire archoelemental's turn, any creature or flammable object within 30 feet of the archoelemental takes 11 (2d10) fire damage and catches fire; until someone takes an action to douse the fire, an ignited target take 5 (1d10) fire damage at the start of each of the archoelemental's turns. Dousing a burning creature will douse any burning objects worn or carried by that creature.
Fire Body. The fire archoelemental can move through a space as narrow as 1 inch wide without squeezing. A creature that touches the archoelemental or hits it with a melee attack while within 5 feet of it takes 11 (2d10) fire damage. Nonmagical weapons that hit the fire archoelemental are destroyed by fire immediately after dealing damage to it.
Legendary Actions
Smoke Cloud (Costs 2 Actions). The fire archoelemental exhales a [
40?]-foot-radius sphere of smoke and embers centered on a point within [
40?] feet of itself. The sphere spreads around corners, and its area is heavily obscured. It lasts for [
1 minute?] or until a wind of moderate or greater speed (at least 10 miles per hour) disperses it. When the cloud appears, any creature in it must make a DC 20 Constitution saving throw or violently cough and choke for 1 round, gaining disadvantage on ability checks. A creature must also make this saving throw when it enters the cloud's area for the first time on a turn or ends its turn there. All standard elementals (air, earth, fire, water) are immune to this choking, as are creatures that do not need to breathe such as undead.