He was holding the source, as he was in The Ways, and has a block that only allows him to embrace the source while being afraid of the dark :P
It was intended by me that they should attack the man, and later discover that he was Padan Fain. Fain was supposed to grow tired of the battle, and run of with the campaigns MacGuffin. But... My players went offpist.
That extra force of 200 lb put Padan Fain over his Heavy Load-limit.
I too thought that only Harden Air would allow players too freeze people in air. But the player went in a rage when I tried to discuss that. So I just let is slip for that session.
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But onto the solution: If the arms try to grip an unwilling, conscious person, they should get a fairly easy reflex check? It would be as evading a physical hand trying to grab you, I think. Or maybe a grapple check from the hand, with the caster's INT/WIS instead of STR.
Other than that, the Arms can be used as whips, dealing damage or pushing objects.