We’re all agreed this should be a fey creature, right? Yeah. So that’s obvious. These don’t count as humanoids, since they’re fey, so I can fit them into this series.
Call this thing we’re making here Elf (Eldest).
Trow: Nasty, Brutish, and Short
A digression on etymology. The word is older than gaming and, like many references to “dark elves” seems to point at what D&D ends up calling dwarves or goblins. Or, frankly, mythologically-speaking, trolls. They do live underground in “trowie knowes”, so I can understand the underdark connection, but it’s at best a jumping off point.
I’m not interested in using the drow to rehabilitate that sensibility. We can just use goblins or something. I’m more interested in using the drow’s stats to represent the same niche the non-SRD Eladrin points at: the sidhe, the Fair Folk, the Others. Call them “Eldest”, the unbroken culture of Chaotic Neutral True Elves.
Elfshot: Drow Sleep Poison’s Mythological Basis
So where did Greyhawk’s drow get their sleep poison? Anglo-Saxon medical journals on elfshot. Why does it knock you unconscious? So that the unfair drow ambush doesn’t end the campaign.
But for the Eldest, that doesn’t work for me. So instead of envenoming their weapons, elven ranged weapon attacks gain this trait:
Elfshot. A creature taking damage from an elfshot weapon must succeed on a DC 13 Constitution saving throw or else become magically intoxicated for 1 minute (1 hour if the saving throw is failed by 5 or more). While intoxicated, the creature suffers disadvantage on intelligence, wisdom and charisma checks and saving throws.
There are countermeasures:
Elfshot countermeasures. If an elfshot wound has iron or steel touched to it (as an action), then the victim can repeat their saving throw against the effect.
Mechanically Modeling the Elvest Eldes
They don’t live underground.
That means they get regular 60 ft. (instead of 120 ft.) darkvision, lose their Sunlight Sensitivity trait, and don’t cast darkness.
Instead of darkness, they cast misty step 1/short rest. There are other abilities we might prefer (particularly invisibility (self only)), but for compatibility with The World’s Greatest Roleplaying Game, this is probably the right move.
But they absolutely need a vulnerability to iron. Damage vulnerability would be overkill (literally; they have only 13 hit points), so instead let’s give them a trait:
Iron Sensitivity. If the elf touches iron or steel, they cannot use their Innate Spellcasting trait, cannot use Elfshot, and has disadvantage on concentration checks until the end of their next turn.
Elves use a lot of brass and bronze and silver and mithril, is all I’m saying.
They don’t envenom their weapons with drow sleep poison, but instead use elfshot, as above.
The arms of the Fair Folk
Standard D&D drow gear is often made of “underdarkium”, and rots on contact with the sunlit lands. So too with the arms of the Eldest; it’s stuff which is enchanted by the glades of Arborea or the moonlit nights of Arvandor, but the same principle applies; 1 hour of sunlight destroys them, as does going more than 30 days without being exposed to moonlight.
The songs of the Fair Folk
Perhaps your drow deal poison damage on their attacks. I recommend that they simply substitute psychic damage (creatures resistant to fear or charm take half damage, creatures immune to fear or charm take none).
This still leaves a band of fair folk in a weird place, because I’ve given them this elfshot ability that makes targets susceptible to mental attack, but have NOT given them any ability to leverage this. Sure, disadvantage on a raft of checks is itself pretty bad; it covers Wisdom (Perception) checks so maybe they can sneak around, etc. Sure, it means that a band of Eldest carries a harpy or a satyr piper or a wizard in their number and makes hay out of the weakened stature of their victims.
But I still might let a band cooperatively create a hypnotic pattern:
A band of at least 5 elves within 30 feet of each other can use their actions to sing and dance cooperatively, concentrating on the effect. If they do so, one of their number casts hypnotic pattern without using a spell slot (if the elf does not already have a saving throw DC, it is 11). An elf may cooperatively concentrate on the effect by spending a bonus action on each of their turns to continue singing and maintain the effect; they cannot rejoin if they stop for any reason and the effect ends if there are not at least 2 elves concentrating on it.
Once an elf has participated in the song, they cannot do so again until they finish a short rest.