Okay here is what we know:
1) Three locations with Odin's Illusionary Rune have been shared.
2) "Odin's Illusionary Rune was used to make the bearer invisible or shape shift, such as the Viking berzerkers who took on the form, strength, and courage of bears in battle" according to a google search.
3) "Originally berserkers developed their own brotherhood of professional l warriors who travelled round and took service with different chiefs. What distinguished them was that they had bears and wolves as totem animals, and clad themselves in their skins. Irrespective of whether it was a bear or a wolf, the warriors believed they were endowed with the spirit of the animal." according from another internet search.
4) " Odin is particularly associated with wolves, ravens, and horses." according to another google search.
5) Thus far, all the runes have been on rock structures.

With all that being said, I tried a few things. I chose to experiment with the symbol located in the southern coastline. I have switched gear attire and weapons: Berserker Gear and Raven Clan Gear. Tried to going berserk (wailing my weapon incessantly) while in having max adrenaline. Used Excalibur and other mythical weapons. Mediation right afterwards, then tried mediating incessantly. I later switched to Noden's Arc and used Incendiary Powder Trap skill and it blacked out the symbol. Long ago I used the explosive arrow with a different bow, there was no explosion and the arrow was just stuck there. Now I did not the chance to try it again with a different bow to see if the result was still the same. I plan on playing again later tonight to search for more Odin's Illusionary Runes.

Pure speculation here and some hope ofcourse.

Seeing how much effort has been put into getting solving the mysterious rune puzzle by the entire community which is been stretching for well over a week and i dont how many gameplay hours combined just a weapon or armor piece wouldn't quite justify the time spent on solving it. Apart from spending time myself into solving this stuff i have also been wondering and hoping would weapon or armor piece could be worth our while.
Then i figured it would be so much cooler if by solving this mysterie i t would actually open a door to an entire new map, like the underworld for example.

So the last 3 item sets of the "ubisoft recoloring store" seem to do absolutely nothing Knight Isu set does nothing, Ullr's set ability dmg remains unchanged and the last set you know apart from the color the Thegn ( sp ) set with the crown does nothing I'm doing lower dmg with it equipped .....