Provender stone

One of the few native plants of Acheron — if it even is truly a plant — the provender stone is an odd fruit. This fruit is a perfect cube, covered in a black, woody rind about a half an inch thick with no patterns or markings, inside of which is a pale white, slightly translucent flesh. The flesh of the provender stone has a very mild taste, dry and just a bit sweet, with a slight coppery aftertaste that fades quickly; it can be fermented, but the resulting brandy has nearly no flavor whatsoever, and any attempt at cooking or drying the flesh simply makes it dissolve. Provender stones are extremely nutritious, able to sustain a person indefinitely on the fruit alone, and is enjoyed by many Acheronians, but most outside the plane consider them too bland to be worth bothering with.

A provender stone grows at a rate of about one inch a day though this seems to slow down after a certain point, and other than the size of the surface on which it grows, seems to have no limit to the size to which it can grow; though a stone will never outgrow its surface, left untouched they've been known to grow to the size of a house, large enough to sustain an entire army alone. Their growth stops as soon as their rind is broken or they're removed from the surface on which they grow, but their flesh never seems to rot, though it does turn opaque after a week or two of exposure to the air. At the exact center of every sufficiently-large provender stone (at least five inches) is a set of eight white, cube-shaped seeds each an inch long arranged in a cubical array. These seeds, when set upon any metallic surface, fade over the course of the next 64 days to black, at which point they "bloom" into stones themselves and begin to grow.

Reference

• Planes of Law: Acheron, pg.4