ToME: the Tales of Maj'Eyal

The Duathedlen Heart appears to give me a light radius of 3, despite listing a -1000 light radius in its description.

Is is from the effect of Infravision? You gain the effect of one light radius for every four infravision, so I would guess that you have between 12 and 15 infravision. This should probably be documented somewhere, but it is working as intended AFAIK.

Ah. Apparently I have 12 infravision, though I don't know where the last 5 are coming from. The heart itself gives 7.

Do you have Heightened Senses? It never comes out and says it, but it gives +infravision.

Then I think it is appropriate to ask for heightened sense's description to mention that it gives infravision as well as being awesome by itself!