hackwings sounds 'rehashible' to me, might fit a clannfear skeleton. i've always wanetd to make a new creature, maybe ill try one of these
But hackwings are birds, right? And clanfears are ground-based...
MMM already has swarms - maybe fleshflies could be like swarms, but damaging health instead?
Well, sloads were included in an TES game - Redguard (well, only one sload N'gasta)
Other missing creatures - Voriplasm "he realized that the pool of green slime in front of them was actually moving, and fairly quickly, from one bank to the other. It deposited small bones behind it as it oozed up into the reeds, and disappeared."
and
Half submerged in the water ahead was a mountain of spines, lying on nine-foot-long claws. White eyes stared blindly forward, and then suddenly the whole creature spasmed and lurched, the jaw of its mouth jutting out, exposing tusks clotted with gore.
"Swamp Leviathan" - both coming from http://www.imperial-library.info/content/oblivion-argonian-account-4.