One minor item of his invention is very popular and others have duplicated its creation. While far from common, they can be found scattered throughout the world.
Called Joh's Crystals, these items always appear to be a piece of polished quartz about 1/2" in diameter. Each crystal has three command words.
The first command word causes the crystal to float in the air near the head of the person who spoke the word and to emit red light. This light does not interfere with infravision or ultravision but is bright enough to allow the user to see clearly to about 4' and faintly another 2', allowing them to negotiate stairs, avoid open pits, etc. It does not work within any form of magical darkness.
The ruddy light is very dim and is only about as visible as a single ember from a fire. It is not bright enough to allow reading, lockpicking, or searching for traps.
The second command word causes the crystal to emit a white light. If the crystal is floating when the command word is uttered it settle's into the hand of the speaker in 1 segment and can then be placed anywhere.
The white light is bright enough to allow reading of even tiny print within 1', reading of normal print within 2', and lock picking, trap finding, etc. out to 5'. It also allows dim vision out to about 10'. Within magical darkness the crystal allows dim vision out to 1'
This light makes the crystal roughly twice as visible as a normal candle. The light is bright enough to disrupt infravision and ultravision.
The third command extinguishes the crystal. I floating when the command is given the crystal takes 1 segment to sink into the speaker's palm.
When floating the crystal has an A.C. of 0 and if struck it is knocked to the ground and immediately extinguished. It saves as any other worn magic item.
The crystal can only emit light (of either sort) for a total of 12 hours in every 24.