I've really liked the derro since 1E's S4 Lost Caverns of Tsojcanth where they made an appearance in the mini-monster manual that accompanied the adventure. Funnily enough, I don't think I have ever actually seen them in play, either with me as the DM or on those very few occasions in the past 32+ years that I have actually been a player.
Scratch that thought: I used them once in a 3.5E campaign and their leader was a half-illithid derro bard who played a small bonethriven (this is an illithid instrument described in 2E's The Illithiad) as his bardic instrument.
They have made an appearance in 4E in Monster Manual 3 but, like practically all the other Underdark monsters in 4E, they're now low- to mid-Paragon Tier creatures. Oh well, not in my Realms. They started with 3 hit dice in 1E so they're going to be level 3 monsters in my games...:
This is the basic derro, a nasty little skirmisher. I haven't thought of a basic racial trait/attack/utility power yet other than them being harmed by sunlight (a 3E innovation, IIRC). It's actually based off the derro miniature I have.
Derro Mad Bolter
I'm rather interested to see what blinding barrage looks like in operation. This could be a rather nasty creature to fight.
For those of us who remember the earlier 1E art for the derro, the crouched derro with the hooked polearm is probably the picture we would remember seeing. Despite it using a polearm, I couldn't justify giving a Small creature reach hence the range being melee 1. It should be an effective soldier with its combination of grab then prone.
One of the random spells that a derro savant could have in 1E was wall of force so I wanted to keep that... even though it seems that it is an Epic-level power in 4E. I kept it anyway. The other powers are based off the 4E version of the savant. In reality, this stat block is very much a work-in-progress that I will review over the next month or so. Of course, by then I may have had a chance to actually playtest it with my group. I'm particularly interested to see if wall of force is game-breaking....