Someone raised the issue of the realms (Essence, Channeling, Mentalism) as being integral to a setting. I’ve already ret-conned my own version of Spell Law to better fit into Shadow World but continually tweak it as my views change or someone raises a compelling argument.
My most recent thought, part of my attempts to REALLY differentiate the realms, is whether Channelers should even be subject to spell failure. If you see all the realms as relatively the same (casting time, casting roll, etc) then this wouldn’t make sense. However, if you see each realm as functioning quite differently, then casting times, casting rolls and even spell failure can be adjusted. That gives each realm clear advantages and disadvantages. If Channeling spells are drawn from a Diety you could make the argument that the caster will either have the spell “bestowed” upon them or not, but it shouldn’t work as capriciously as Essence or Mentalism spells. The outside agency the Diety represents might shield the caster from mundane failures.
It’s just a thought–not fully fleshed out yet but worth pondering further.