If the creatures of he microcosmos were made large, they would be genuinely horrific. Rotifers (there are numerous lineages - the giant one here, if you're interested, is based on a bdelloid rotifer with inch-worming motility, but you may of course vary that and make swimming or even sessile varieties). They are tough, near indiscriminate, nearly ineradicable predators. And for such simple organisms the show a surprising range of behaviours.
Rotifer, Giant
by Cab Davidson
| Stat | Rotifer, Giant |
| AC: | 6 |
| HD: | 7+3* |
| Movement (squirming): | 60’ (20’) |
| Attacks: | 1 suck |
| Damage: | 0 (10d10) |
| Number Appearing: | 1 (1) |
| Save As: | Fighter 4 |
| Morale: | 12 |
| Treasure Type: | Vx2 |
| Intelligence: | 0 |
| XP Value: | 1025 |
Rotifers are common, tiny, predatory animals found across the world in ponds, rivers, lakes and indeed anywhere there is a body of water. The giant rotifer is rather akin to a giant, muscular jellyfish, with a single powerful foot with which it holds on to a surface, and at the other end of its body (15’ away) it has something akin to a head, with masses of beating arms generating a current towards its mouth. That current drags anything in the water towards it, at a tremendous rate, where that prey is eventually crushed and swallowed.
Giant rotifers do not target any prey, they merely suck water towards them. That creates a cone, 100’ long and 50’ wide at the far end. Any creatures therein must make a saving throw vs. dragon breath or be caught in the cone, and be dragged at increasing rate towards the mouth of the beast. In the first round their motion is deflected by 10’ from their chosen course, towards the rotifer. In the second round they are drawn a further 70’ towards the rotifer, and in the third, if they have not already entered the mouthparts of the rotifer, they are consumed.
The only hard part of the rotifers body is a ring of horrific tooth like extrusions in its neck, called a mastax. Being chewed by a mastax causes horrific (10d10) damage, and in the unlikely scenario of surviving ingestion a character takes a further 2d8 damage per round from digestive juices. Giant rotifers are found in the deepest, darkest lakes, most often underground in the most cursed locations. It is unknown what process causes a rotifer to grow to such a size or indeed whether they are the same kind of life form as other rotifers.
While most giant rotifers are unable to swim, they move along the walls and floors of their habitats by holding on in a direction of travel with their heads, and bringing their foot closer to it. Thus this horrific predator perambulates rather like an inch worm. However it is only when in motion that the arms of the rotifer are not creating deadly currents towards their maws.
Sages have speculated that they may be from an outer plane dominated by gargantuan animalcules. If that is true, no explorers have returned from said plane to tell the tale.