The King said:
[...] but it is then fair to suppose that elfsense (know as the Song of Aldrya) is linked in a similar manner to the plant rune. Then how useful is this sense to an Aldryami which doesn't live among plants anymore?
Fair or not, I believe following this line of thought would be very interesting. Perhaps in another thread?
The King said:
Of course it would have been far better if darksense had been definied with one more sentence in the MRQ guide to the trolls as to whether the sense functions in daylight or not.
Yes, such information would have been essential when playing meetings with the Dark Men.
IMHO, darksense does function in ordinary daylight. In the celestial world things might be different, though, because Darkness is mythically very weak there. Literally, there might be no Darkness to sense there - in a similar manner as eyes would be useless in the Darkness of primal Hell, in that place which is Subere and utterly devoid of Light/Fire.
You could devise a simple table to represent the changing utility of darksense in relation to the presence of Light/Fire. For example:
Mythical Light/Fire ----> useless
Clear/Bright day ------> x 0,25
Ordinary day ----------> x 0,5 (RQ spell Lightwall)
Cloudy day ------------> x 0,75
Dusk/dawn ------------> x 0,8...0,9
Ordinary night ---------> x 1,0
Dark night -------------> x 1,25
Deep underground ----> x 1,5 (RQ spell Darkwall)
Mythical Darkness ----> x 2,0
For example, Tagtaz the Troll, with Darksense/Scan 48%, would only have Darksense/Scan 24% in full daylight or spell-light. On the other hand, in his deep underground lair, Tagzat would have Darksense/Scan 72%. If he would ever enter that part of the Underworld which is unmolested by Light/Fire, he would have Darksense/Scan 96% - he would be able to sense Darkness with divine accuracy, because he would be surrounded with divinely accurate Darkness.
In this way, trolls living on Hurtplace (surface world) would be less alert in daylight but more alert in the darkest hours of the night. Also, some regions of Glorantha infested with Darkness (e.g. Dagori Inkarth, the realm of Gore & Gash & Kyger Litor herself, and Shadow Plateau, the realm of Argan Argar) might be perpetually more dark than ordinary places; this could be represented with adding 0,25 to the Darksense multiple.
In addition, trolls who plan to face enemies of the Light/Fire tribe would need to train their eyesight or use potent Darkness magic, because otherwise they would probably be "blinded" by the brightness of their enemies.
(The other side of the coin is that beings depending on eyesight would need to train their other senses or bring sources of light or Light/Fire magic with them if they wish to see in Darkness. Just like we tend to do when burning fires & lights in darkness in order to see - it's obvious. The point is that in a world of myth, Darkness is not a simple result of lack of Light/Fire.)
IMHO, YGWV.
-Ilkka