The size category Fine includes things 6" and smaller, but is there a point at which things are so little that they are no longer limited by the constraints of the size category Fine? That is, can a square hold only the same number of Fine creatures as Fine rocks, grains of sand, or even atoms?

Here's the plan: A psion wants to manifests the 9th-level psion/wilder power microcosm [telepathy] (Expanded Psionics Handbook 118) so as to secure as many creatures within the shared reality as possible. He wants to keep the affected creatures that share that reality alive and preserved in quintessence created by the 4th-level shaper power quintessence [metacreativity] (XPH 128), probably in a backpack or something. He also plans to visit that shared reality on occasion using, for example, the 4th-level oneiromancy spell dream walk [conj] (Heroes of Horror 129) or the 9th-level psion/wilder power reality revision [clairsentience] (XPH 128-9).

So were the creatures that are to be secured in the shared reality created by the power microcosm to manifest first the 4th-level power metamorphosis [psychometabolism] (XPH 116-7) to assume the forms of germs, grains of sand, or subatomic particles then reduced to 0 hp or less but not slain, would the psion be able to affect with the microcosm power more of these infinitesimally little creatures than he would have affected were the creatures either to possess the size category Fine naturally or to have manifested the metamorphosis power to assume the form of creatures of Fine size?

For example, can 2 billion of these grains-of-sand creatures be compacted into 2 cu. ft. so that they could all be affected by a lone manifestation of the power microcosm, slathered with quintessence, and stored in a typical backpack?

  • \$\begingroup\$ Wondering how big my microcosm could be from a people stand point if the people's size isn't a factor (like if they're a -1 hp grain of sand) \$\endgroup\$
    – Cellheim
    Jul 15, 2017 at 14:38
  • \$\begingroup\$ I'll edit to include my intentions. Basically microcosm has a radius of 15 feet so if I shrink people small enough and they automatically fail to resist because of -1hp can I have millions of metamorphed followers all in the same microcosm? \$\endgroup\$
    – Cellheim
    Jul 15, 2017 at 20:29
  • \$\begingroup\$ I made a serious edit to this question. I hope that's okay. I think this is what you're after based on comments (and my failed answer!). If it's not, please rollback or edit it further. It's an interesting question from a game-design point of view. (However, I still don't know how the psion would get all his future inhabitants to manifest metamorphosis nor how the psion would so precisely reduce their hp to 0 or less without killing them—those would probably make (ahem) fine standalone questions.) \$\endgroup\$ Jul 16, 2017 at 13:01

2 Answers 2


What you ask is in fact irrelevant to what you want to accomplish.

Those rules for sharing squares and size catigories are for combat purposes. The common amount of space mentioned in the rules is needed by a fine creature to conduct combat - swing weapons, dodge blows, perform tricks, etc - on a reasonably flat surface.

When the question is: "is it OK to store people in piles?", the answer will be: "yes, it is OK1, if they are willing to do so or are helpless". How many you can store is the question of real physical volume their bodies occupy.

So the answer is:

Yes, 2 billion creatures potentially may fit into an area of Microcosm power.

1: It is generally OK. But if the combat suddenly starts, we just can't realy say what happens when those piled humans will become attacked and so on. And it is out of the sope of this question. And... gods of Good will look at you with suspicion at least.

  • \$\begingroup\$ In that case you either have enough space to be squeezing (d20srd.org/srd/combat/…) or you need to make escape artist checks. \$\endgroup\$
    – fectin
    Jul 26, 2017 at 2:11

While you can assume any physical size, you can't assume any size smaller than Fine, which means the mechanics of very small forms may be disappointing for you. For example, let's assume you take the form of a sand atom (i.e. the smallest possible unit of sand, which if it were in any way divided into parts would no longer be sand). You might think such an entity would be hard to see, and you are somewhat accurate: being of size Fine provides a +16 size bonus on Hide checks. However, a Fine-sized pencil, an ant, a pebble, and a gold piece all have that same bonus. Furthermore, a dagger sized for a Silthilar (Lords of Madness, Page 169) is two size categories smaller than said atom, despite probably being at least a bit larger in terms of actual size.

Not all mechanics depend on Size Category rather than physical characteristics like height and weight-- some traps are still triggered by pressure plates with a weight limit rather than a size limit, and many spells effects are contingent upon volumetric considerations. Nonetheless, the vast majority of mechanics care about Size Category rather that how small you actually are. Even in a game with physical laws similar to those currently thought to apply to the real world by most people, turning into a water molecule doesn't make you invisible, nor render you particularly difficult to notice without a Hide or Disguise check on your part.

A good example of mechanics that depend solely upon Size Category and not actual volume are the rules governing the number of creatures that can fit in a given area. For very small creatures the relevant rule is as follows:

Very small creatures take up less than 1 square of space. This means that more than one such creature can fit into a single square. A Tiny creature typically occupies a space only 2½ feet across, so four can fit into a single square. Twenty-five Diminutive creatures or 100 Fine creatures can fit into a single square.

No matter how small you make a creature, without some other special ability or interaction with some unusual ruleset you can only fit 100 creatures in a space. This means you can fit 2,400 creatures in a 15ft radius burst. Notably, if the members can instead count as a swarm of Fine creatures, you can touch 12 swarms with your microcosm (and touching a single square of a swarm is good enough to get all the creatures in it), garnering 120,000 creatures. Unfortunately, a swarm at 0 hp reverts to the individual creatures it is composed of, so you'd have to use swarms as 1 hp instead, which would require you to be able to affect 12 hp worth of creatures to get the whole 120,000. Of course, even the base spell can do that, so you shouldn't have much trouble with that method.

Now, the reason you can't go smaller than Fine isn't that nothing is that small! As mentioned, light weapons for Fine creatures are smaller than Fine, as are reduced Fine creatures, a Small or smaller object affected by Shrink Item, and normal-sized spider affected by an opposite-effect Giant Vermin spell. The reason you can't get anything smaller than Fine is because metamorphasis states:

You can’t assume a form smaller than Fine.

So you can't. RAW all Fine forms have the same size stats, and any attempt to argue that a certain form is so small it should get the stats of a form smaller than Fine is an argument that that form should be considered smaller than Fine and disallowed. You can't have your cake and eat it, too.

  • 1
    \$\begingroup\$ Just an aside, one of my favorite Dungeon Master's Guide quotations: "The Material Plane tends to be the most Earthlike of all planes and operates under the same set of natural laws that our own real world does" (147). \$\endgroup\$ Jul 15, 2017 at 19:28
  • \$\begingroup\$ @the dark wanderer sorry I should have included why I wanted to do this. It to fit people into a power radius. \$\endgroup\$
    – Cellheim
    Jul 15, 2017 at 20:39
  • \$\begingroup\$ Wouldnt item size rules govern how many could fit into a space if they all metamorphosis themselves? \$\endgroup\$
    – Cellheim
    Jul 15, 2017 at 22:22

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