Brief summary - so the original Shamir was this worm that King Solomon was supposed to have used to do the stonework for the Temple in Jerusalem. This was a way of reconciling the fact that it was obviously made of cut stone with the fact that tradition said that the sound of cutting stone was not heard when it was being constructed, and that iron tools were forbidden (as being too similar to weapons) on the Temple mount. Later another rabbi came along and pointed out that that probably just meant that they cut the stone off-site and hauled it in. Obviously the theory that Solomon had a magic worm is much cooler that the boring explanation. Accordingly, there are lots of stories about how he got the shamir and what it could do and so on.
Anyway, there is obviously a lot of controversy about the details of this supposed object in real life, but the equivalent thing in the PRPG universe is a bit better known, so here are its properties in brief:
- It is an alchemically-created synthetic lifeform, like a homunculus.
- It is made of corundum and pitchblende, plus other reagents not known to Akasha (or most anyone else - they are very rare.)
- It will annihilate up to 30 cubic centimetres of stone or metal per turn if it is brought within a meter of them and has a line of sight. If more than that is present, then it prefers to cut out thin planes of that volume.
- Its cutting action can be controlled by painting or finishing the surface; it will only gaze upon and annihilate the unfinished metal or stone.
- It cannot affect the metal lead.
- It has a finite number of uses, which are not determinable by examination.
- It can be reinvigorated by distilling it with a special potion, not known to Akasha or modern alchemy generally, but which might be re-discoverable.
It's in a wooden box (8 cm high, 12cm by 12cm wide/deep), with an inner liner of lead glued to the wood. In the box is a folded pad of wool, on which is the shamir.
It definitely has uses in reagent preparation, including of materials that would ordinarily be too difficult to process into proper form for alchemical reagents in the field, e.g. metals and stones which need large milling apparatus to reduce to powders ordinarily. With the shamir you could just collect the dust/vapor they get turned into. Maybe those reagents would have applications in alchemically improving armors, making some sort of 'stoneskin' potion, or something along those lines -- just some thoughts.
6-7 uses left.