Mad carthos has spiritwalk and Karnon is immune to frost and fear. when Mad Carthos makes a spiritwalk attack though Karnon, does that attack gain the benefit of Karnon frost and fear immunity...?

Spiritwalker makes the attack work "as though you were in that space", not as if the other hero were making the attack. You don't use the other hero's items, traits, skills, or abilities - just their location.

many thanks...my time as OL has just improved :-)