Its been a while since I read RoW so I may be wrong on some of this, but this thought came up when reading another post.

RoW - All & Mistborn Secret History
  1. Do we know what happens when a godmetal is taken into the cognitive realm?
  2. We know that lower spren have a presence in both the physical and cognitive realm - do bonded spren have a visible presence in the cognitive realm when they are in the physical? In M:SH people show up as lights in the cognitive realm.
  3. if you can take one of those god metal (or inverted god metal) assassin blades into the cognitive realm, could you kill A) spren B) people using them?