The Storm Giant has a STR score of 29. According to the encumbrance rules that means the maximum weight a giant could lift is 435 lb. which really isn't that much.
To put it in perspective. The Storm giant is 5x taller than a human, at the same proportion and thus has about 25x more mass. An average human male weighs around 180lb. A Storm Giant thus weighs around 4500 lb. So it's impossible for one Storm Giant to carry another.
Another way of looking at it. A human-scale sword might be around 4ft. long and weigh 3 pounds. However, a sword that's long enough for a Storm Giant would need to be around 20 ft. long and to maintain its own integrity would need to be about 2 inches thick at its centre and might be a foot wide. A sword like that would weight about 800 lb.
To even be able to wield a sword like that without being encumbered, the Storm Giant would need a minimum STR score of 160.
So in conclusion, Storm Giants must be about the weakest creatures in the Multi-verse on a pound for pound basis 😛
Am I missing some encumbrance rule somewhere that adjusts this based on creature size category?
Best Answer
Storm Giants are Huge creatures, not Medium.
The encumbrance rules neglect the size of a creature when calculating if it is encumbered or heavily encumbered. While this is true, the maximum capacity of a Storm Giant is not the same that a human would have given it a Strength score of 29.
Quoting the rules on lifting and carrying (Player's Handbook, page 176):
The rules on creature size categories are on page 191 of the Player's Handbook:
\$\begin{array}{|l|c|} \hline \textbf{Size} & \textbf{Space} \\ \hline \text{Tiny} & 2\,\frac{1}{2}\,\text{by}\,2\,\frac{1}{2}\,\text{ft.} \\ \text{Small} & 5\,\text{by}\,5\,\text{ft.} \\ \text{Medium} & 5\,\text{by}\,5\,\text{ft.} \\ \text{Large} & 10\,\text{by}\,10\,\text{ft.} \\ \text{Huge} & 15\,\text{by}\,15\,\text{ft.} \\ \text{Gargantuan} & 20\,\text{by}\,20\,\text{ft. or larger} \\ \hline \end{array} \$
Huge size is two size categories above Medium size; therefore, the maximum weight a storm giant could lift is not 435 lbs., but four times that (i.e. 435 lbs., doubled twice): a total of 1,740 lbs.
Remember that the Encumbrance rules are a variant rule and are meant to apply to playable races (Small- to Medium-sized creatures). The DM is free to adjust those values to be doubled for each size above Medium to keep it plausible to be used for larger creatures, to mirror the increase in carrying capacity for larger sizes.
Also, they are monsters. The rules for players do not necessarily apply the same way for NPCs.