Advantage: sacrificing riposte question

[jdizzy001]

In order to use this ability the player must pass a dex check. The entry does not specifiy the CL of this check. I am assuming the CL = HD of the intended target, but since other advantages specifically stated what the CL was for using advantages, I thought I'd ask for clarification. What is the CL on the dex check to use sacrificing riposte?

[Arduin]

Logic (as far as that can be used in a FRPG) dictates the difficulty of such a move is based on the opponent...

[edit] Ya know if vs. a PC class you might want to use the opponents to hit bonus rather than class level as the difficulty level...

[serleran]

Either HD, BtH, or AC could be considered.

Against monsters, HD = BtH generally, so wouldn't matter so much. Against AC would be ridiculously difficult considered it starts at 10 and increases more than it decreases.

So, BtH would be my ruling primarily as it makes the most sense.