I'm guessing by now some (or possibly all !!) of you have noticed what is (EDIT: PERHAPS) a nasty little combo. Get a couple of cheap serpents in your discard and it's a :

Opponent must sacrifice a character of cost 0 or higher every phase.

Though about it, and am wondering (and I guess a little hoping) that the reference to PRINTED cost of Cthylla's victim also carries over to the sacrificed. Which hinges on the question, does on insane character even have a 'printed' cost of 0 ? or is simply a 0 cost with no skill value printed on its backside (as per the FAQ) ?, which then moves this discussion over to what are your thoughts on this ? and that I'm now in the wrong forum. oops.

My understanding is that an insane character does not have a printed cost (or a "printed" anything else). See the card back? Is there any printed cost on it? Then there's your answer.

So, while you can still sac the character, your opponent will never have any characters meeting the criteria because the comparison of printed skill is not meaningful. You still might get some other benefit from the original sacrifice though, so it's important to note that that part still works.

Yes, I second that. Although the FAQ section on "printed" is ambiguous, in the passage about Doppelgänger it is clarified that insane characters don't have a printed cost:

Can Doppelganger copy an insane
character?
No. Doppelganger reads, “When
you play Doppelganger from your
hand choose a non-unique character
in play. X is equal to the printed
cost of that character.” and insane
characters have no printed cost there

is no way to determine the cost to play
Doppelganger. Thus, Doppelganger
cannot copy a an insane character.