Artificer 9/Cannith Wand Adept 3. Or was it Heir of Siberys 3? Point is, 12 levels and not a good build.
Also, Lifesight means light shines from them. Which means when they are mostly covered in snow, you still see light, but no you can't tell that oh yeah, it's Large. In any case, the scout doesn't get to metagame, and suddenly become aware of something there and not go ahead. Either he's there, he attempts to do his job, and he fails, he's there, he does not attempt to do his job, and the discussion is moot, or he is not there, and the party is better for it (and the discussion is moot).
As it is now, this discussion is primarily serving to amuse the players, who by the way I fully expect to slaughter the so called level 18, but really just level 13 Ice Devil despite the fact said Ice Devil is competent, because they too are competent. What a novel concept, adventurers that can do their fucking jobs, take on adversity, and win.
Oh and you cast Fireball? Ok. You melt the snow. There is now an unharmed Ice Devil standing there. Since you wasted your surprise round, not only with pewpewpew but with pewpewpew it's immune to it destroys you.
Psst... BeholderSlayer, Lifesight is the undead one. Not Mindsight.