In "Drow of the Underdark", p. 90, there is an NPC with the special ability "burning faerie fire". Where do I find the rules on this ability?
I am not aware of any ability by that name, nor does anything in Dak Falshae’s statblock indicate how he would have gotten it (which we might be able to trace back to its source). None of his class levels, feats, or items offer an ability called burning faerie fire.
Moreover, I can also tell you that burning faerie fire is not described anywhere in Drow of the Underdark—the word “burning” appears thirteen times in the book, and none of them describe this. We have:
- twice for burning faerie fire in the aforementioned NPC’s statblock, but only a mention, not a description,
- the “burning desire” of kinslayers (the prestige class that Dak is an example of) to make an unholy pact with Lolth,
- five mentions of the burning hands spell,
- a reference to the “burning” feeling of poison,
- a translation of the name Molv as “burning, fire, of fire,”
- the “burning abhorrence” that elves and drow feel for one another,
- how curtain of darkness cannot put out a burning building,
- that burning can be a solution to the webs from an arachnid rod, and
- a description of some lava-filled cavern as a “burning cauldron.”
And general searching beyond Drow of the Underdark finds no other reference to the concept beyond Dak Falshae’s statblock.
All of which amounts to a simple fact: NPC statblocks in D&D 3.5e are notoriously unreliable. They have errors all the time. Wizards of the Coast didn’t seem to consider them terribly important or valuable, and so they seem to have never gotten any careful scrutiny or editing. What almost certainly happened in this case is that an earlier draft of the kinslayer prestige class included an ability called burning faerie fire, and so Dak included it, and then a later revision removed it but did not update Dak. Very much par for the course, as NPC statblocks go. At least he actually qualifies for kinslayer; many prestige class example NPCs fail to even meet that first hurdle of serving as an example of the prestige class.