Is the mask of King Strohm, from the Windspear Hills quest (the maze) good for anything?

Except for the quest related use, nah. Thiefs can wear it to prevent critical hit damage

Are you sure Arak? It's a mask not a helmet. I don't think it protects your scone at all.
I assume Burner that you've already 'seen' the problem Strohms mask solves.

Keep it as a souvenier in your stronghold.

or if you have true sight.....................

Yes, it prevents critical hits.