If overlord use dark charm on my hero who has weapon Bow of Bone can overlord use passive ability of this bow?
Bow of Bone: "If you have not moved this turn, add 1 additional green power die to your attack pool"

I think he cant because text refer only to heros turn, right? But he thinks otherwise. I need a definitive answer. Thanks guys.

Dark Charm

Quote

Play this card on a hero at the start of your turn [...]

=> OL Turn

Bow of Bone

Quote

"If you have not moved this turn [...]"

=> Hero X Turn

Turn <> Round
1 Round = Hero 1 turn + Hero 2 turn + Hero 3 turn + Hero 4 turn + OL turn

cf rule book p7 top left

Short answer Dark Charm doesn't impact Bow of Bones

Agreed. Bow of Bone will get the green die on OL turn, assuming hero hasn't moved during OL turn. OLs are players just like the heroes, and have a turn, similar to the heroes.