V's Deal: The Full Consequences

[Thrillhouse]

(I should clarify I don't play DND)

But something rather big is being missed here. Specifically, this here:
http://www.giantitp.com/comics/oots0634.html

Right before V is about to take the deal, one of the fiends STOPS him/her and proposes a completely viable alternate plan. If the plan is only to get V to attack Xykon so he'll get moving and to gain control of someone near the gates, why risk this? They must have NEEDED V to take the power for selfish reasons.

Furthermore, this comic provides another key piece of information:
http://www.giantitp.com/comics/oots0640.html

First, we have the fiends saying that they LIED about the "alignment feedback" because "A good way to get a decent person to something horrible is to convince them that they're not responsible for their actions." This, combined with the alternate plan, suggests that CORRUPTING V is also a part of this plan, and given the risk they took by offering the alternate plan, a SIGNIFICANT part of the plan. (Significant enough that it was worth risking V's refusal)

So, what might the reason be? One possibility is that the Familicide spell was a part of the plan, but I think we can easily dismiss this. Sure, they would have known that Haaerta could cast the spell. But just hoping that V would cast it, and not some other spell, seems very unlikely, unless Haaerta is in on the plan and was asked to suggest it. But more importantly, we can clearly see that the fiends are SHOCKED when V uses Familicide in the second comic I linked.

Instead, I would propose that this is a much longer term action that we cannot entirely predict. Recall that the fiends had psychological profilers analyze V's actions and determined that he was likely to attack the most powerful available foe, given enough power(Xykon). It's not inconcievable that they've also looked into how V might respond, long term, to an action of great evil on his/her part, (or how his/her moral character could be corrupted) which would explain why the deal needed to be done, as the comic title reads, "For the Wrong Reasons".