Creeping Doom - Large Swarm of Tiny Beasts (CR 8)

Who remembers the spell Creeping Doom? No, not the reigned in 3rd and 4th edition ones, I mean the earlier ones that could inflict 1d6+4 x 100 points of damage, that one?


No, this one is nothing like that. Cool though wasn't it? I fondly remember some 26th level (or so) heroes in my 2nd Edition AD&D game facing off against a Yochlol, in the heart of a dwaer'syth's spelljamming vessel, and things coming unstuck really quickly when it vomited a double strength Creeping Doom at them (Traveller teleported back to his own ship, leaving poor old King Brundor to take the brunt himself. He was skeletonised...not for the first or indeed, last time).
"Ha ha ha! This is fun. The pain is excruciating."

Anyway, this may or may not have been created because one of my groups are in the middle of (loudly) infiltrating a dwaer'syth house compound, and are very likely to face against Creeping Dooms, and those able to summon them.

Obvious variants would have climbing or flying speeds, and may be poisonous.

You may have noted that I have taken quite a few cues from 4e's swarms. That's because I actually think 4e did swarms perfectly. Swarms are, and should be seen as, terrifying things.