The exact wording of Dark charm is as follows:
"Play this card on a hero at the start of your turn. The hero tests (willpower). If he passes, draw 1 Overlord card. If he fails, you may perform a move or attack action with that hero as if he were one of your monsters this turn. You cannot force him to suffer (fatigue) or us a Potion, but you may force him to attack himself."
The "as if" is important, if we are being careful about interpreting this rule. Treating something "as if" it is something else does not change the properties of that thing. If I treat an orange "as if" it is a cinder block, and try to use it to prop up the axle of my car so I can remove the wheel and examine the breaks, the orange does not suddenly take on the density of a cinder block and will be crushed by the axle. By this reasoning treating a hero "as if" it is a monster for purposes of control, does not necessarily mean it ceases to be a hero for all other purposes.
The contradictory rulings above are also troubling:
- That a DC'ed hero can move through monsters.
- That a DC'ed hero is able to be targeted by Overlord buff cards.
For 1., moving through other monsters seems thematically appropriate, because monsters may recognize that the hero is under the Overlord's power, and let him or her pass.
For 2., that a hero under the Overlord's power might benefit from a further buff spell also seems appropriate for the limited amount of time he or she is influenced.
What is more important in the case of the wendigo's freezing aura is that DC states that you cannot force a hero to suffer fatigue. This means either that moving a hero adjacent to a wendigo will not cause them to suffer fatigue, or that you cannot force a hero to move adjacent to a wendigo because he would suffer fatigue. I think it is the latter, because it makes more sense thematically. You cannot force a hero to do something that takes more effort than a simple move action or attack.
However, this does not solve the porblem with respect to other auras like that of a Demon Lord which causes a hero to suffer damage. So the question is can you move a hero and cause them to suffer damage? You can move them into an obstacle like lava, pits, etc. So it would seem that moving them adjacent to a damage aura monster is a similar case. And forcing a hero to suffer damage is what you do with DC when you force a hero to attack themselves.
So, according to my understanding, DC allows the Overlord to treat a hero "as if" it were a monster for one action, which may be a move action or an attack. During that action the hero's movement is not blocked by monster figures, and that hero may be the target of overlord cards that trigger when a monster takes a move action or performs an attack. And that hero may be forced to suffer damage by either entering spaces or a self-targeted attack, but that hero may not take any action that would force him or her to suffer fatigue, including entering spaces, or use a potion.