If we take a look at the Humanoids in the Monster Manual we see that all of them are either creature size Medium or Small. I personally presume this is because Humanoids are what most player characters are and playable races are by design always small or medium. We can find a similiar situation if we look at Giants. All of them are of the sizes Large, Huge or Gargantuan (there are no Gargantuan Giants in the MM, but there are in Glory of the Giants). One could argue, that Giants are Humanoids who are to big to be classified as such. The introduction of the MM even says "Giants tower over humans and their kind [i.e humanoids]".
This gets even more interesting if we look at two tall races that are supposedly related to Giants: the Firbolgs and the Goliaths. Neither of them have the Giant creature type, as both are humanoids, be it as player characters or as monster statblocks. And it would seem that this is because they are of size category Medium, a category that Giants are supposedly banned from. And then if we look at the Half-Ogre, we get the same thing in reverse, this Half-Humanoid & Half-Giant, is still considered a Giant, and it would seem to be because it boasts the Large creature size.
Regardless of the reasoning for this, the game heavily implies that Humanoids and Giants can only exist in specific size categories and not in any others, Small and Medium for the former and Large, Huge and Gargantuan for the latter. However as far as I could find, this fact is never outright stated as such. The closest thing I could find are the descriptions of the creature types in the third Edition SRD. Where it says that humanoids "usually are Small or Medium-size" and Giants are "usually of at least Large size".
The word 'usually' here intrigues me, as it suggest there might be Humanoids and Giants that defy these Size Categories and would therefore disprove my theory of them being mechanically defined by their sizes. Which is why I am asking: Can anyone tell me any prove or disprove on the implication that the Humanoid and Giant creature types are limited to certain size categories?
This might be:
- Any official statements that outright state that this is or is not the case.*
- Any Humanoid or Giant Statblocks or Playable Races that defy these rules.**
These preferably from official sources pertaining 5E, if not than I would also accept something from an earlier edition of the game or officially promoted 5E Fan Content (e.g. Kobold Press).
*Not counting of course the aforementioned descriptions in the MM and the 3E SRD, as these both seem to kinda dodge the question and don't answer it directly, leaving us in the dark. The MM one being more of a description than a rule and the 3E one sounding just vague enough for them to leave the possibility open to defy these rules if they want to in the future.
**Of course eligible creatures would only include average adults of their respective races, as we can assume that humanoids babies would be classified as tiny humanoids and we learn from Glory of the Giants that children of true giants are medium-sized Giants. And we of course must also limit it to Creatures in their default state, unaffected by Magic or other Abilities that change their Size. As we know that both the Runecarver Fighter and Path of the Giant Barbarian can increase their sizes to large and beyond, while still being humanoids and so can a medium Wizard that casts Enlarge on themself.
