Smastan
Smastan berries are bright red fruit that temporarily but rapidly shrink the person who eats them to six inches. They still exist mechanically in the game, but in the modern usage, smastan berries are just food and have no magical properties. At one point, they were able to temporarily but rapidly shrink the person who eats them to six inches, however the lore was later updated to note that those effects were an aberration that is not normal for the species.
See the Elanthian Flora Guide for full information.
Shrinking
>look bush The bush grows very low to the ground and has waxy green leaves with red berries. It is very rare. >look berries The berries look ripe and sweet. >take berries You can't just get them, they're too firmly attached to the branch. Perhaps if you plucked them, they would come free. >pluck berries You pluck the smastan berries briskly, and a sudden impulse causes you to stuff them completely in your mouth and gobble them down. No sooner do you swallow the smastan berries, than you feel your whole body tingle. You realize you are now only 6 inches tall and quickly clamber through the narrow fissure. You panic momentarily, terrified at being caught a little short but you quickly return to normal size and look around. >look bush The smastan bush here is contained in a plain fired clay pot. It looks remarkably healthy for an extremely rare plant generally only found in the wild.
Behind the Scenes
Smastan berries do not seem to originate in a Shadow World source book, but the same word was used for them both now and previously. They are used to enter the Ye Oddity Workshop, which was originally owned by Lord Odds Bodkins as a private workshop. The word "smastan" may be Seoltang; it appears to be constructed from the (glossary adjacent) word parts "sma" and "stan", presumably meaning something to the effect of "tiny pest."