A rewrite of the 2nd level druid spell, Produce Flame, which is a convoluted, fairly weak 2nd level spell that does not differ much in principle from Flame Blade. I must admit, there are obvious reasons why a simple spell like this described below was not included in the early game:
Duration: see below
Area of Effect: 3' diameter; see below
Casting Time: 1 round
Saving Throw: none
Level: druid (2nd)
Creates an inflamed jumble of six fire logs in full burn, with a hot bed of coals and embers, in the manner typical of a campfire or fireplace. As the logs are already alight, the fire will be hot enough to dry and burn even the wettest of wood, so that the fire can be sustained even in a light rain (a moderate or heavy rain will inevitably drown the fire).
If cast indoors, in a thoroughly dry environment or among combustibles, the fire produced will set the area ablaze, spreading to walls, ceilings, drapery, furniture, brush or dry grass, quickly getting out of control. In these circumstances, presume the fire will spread to set the originating hex on fire in the 1st round; that it will spread to all adjacent hexes within the next 1-3 rounds; and finally that it will have a 25' diameter circle freely burning within 2-8 rounds. From that point forward, the fire would likely consume 2-7 additional 5 foot hexes per round.
If cast into a hex including an individual, the fire will cause 2-7 damage before the victim can jump out of the flames; their boots and clothing should roll save vs. fire damage (a failure of 5 below that needed indicates that these have caught on fire).
(Note: the reason why a spell like wasn't included in AD&D is due to the obvious abuse of players seeking careers as an arsonist; I believe, however, that responsible players are able to see the downside of continually taking such action - moreover, I feel that a world with magic would know how to deal with such persons).