Hi,
New to the board, long time WoT fan, new Sanderson fan- just read TWOK.
I've been lurking in this section trying to make sense of the magic systems in the cosmere and here's my idea;
Tanavast or what's left of his power is the Highstorm in the same way that the Mist was the body of Preservation.
"I've come to your land to chase an old acquaintance, but I end up spending most of my time hiding from him instead"
-Hoid, TWOK pg. 807
This might also explain why Dalinar and Kaladin have visions when there is a highstorm overhead- the remnant power of Honor/Tanavast is at its peak.
This would explain why the Shin believe that Stormlight is holy.
This could then be extrapolated to the magic system; Honorable Intent grants powers e.g. binding (Szeth bound by his Oath) is the basis of surgebinding, Telling the Truth (an Honorable thing) powers Travelling (Shallan) and Defending those who cannot defend themselves (Kaladin) Windrunning and Soulcasting/ Transformation (Jasnah) a historian who seeks Truth (also accesses her power when she believes she is protecting others).
What do you think?