so whats the big deal with this card exactly? what can this do that infernal obsession can not?

kamacausey said:

Not much. Just cheaper to play and you have possibility of potentially redrawing it. It also can trigger a deck shuffle which sometimes is good.

Someone said that when the character goes insane that you get to keep them. Is that true? I know when infernal obsession goes away you lose that character.

Literal text would indicate that, but I think there was a ruling that attachments apply their passive only as long as they are attached.
I don't know is it official though.

link to the thread:

http://www.fantasyflightgames.com/edge_foros_discusion.asp?efid=37&efcid=4&efidt=637379

kamacausey said:

There was some discussion about this and it was played wrong in at least one tournament, but in the meantime Damon clarified that the effect ends when Stygian Eye leaves play.

Browsed previous thread:

Take control is permanent with triggered effects. Stygians is passive so it lasts only as long as its attached.

There was some discussion on Repo mans passive granting control but the consensus was that his is permanent as you cant undo winning a struggle.
(I think this explanation is not perfect, but results makes sens to me.)

THe ruling is based on what is causing the shift of control. As long as that state is still true the control stays. When it is an attachment that shifts control when it is attached, when it becomes unattached that condition is no longer true so control shifts back. When it is because you won a struggle as long as that condition is still true the control remains until it is no longer true… since you cannot lose a challenge that you have already won (at least not yet ) that condition is always true.

-removed-

[edit] ok re read - passives have no default duration with current FAQ wording - i think they should behave like all other cards and just mention attachments as an exception, but my argument about Repo man is invalid

or maybe passives are that special as far as duration is concerned, if so it should be stated that this paragraph doesn't refer to passives

So when the character you took with stygian eye goes insane the insane character goes back to the owners controller right?

Yes, when attachment is removed (for example by going insane) character control goes back to the owner.