:lol:
On what?!?
No Prisoners, in a nutshell, gives a -1DV penalty and a -1ATT penalty to "all opponents". I know it says AC, but there's no AC in Conan, so that obviously means DV. It was probably copy/pasted from another source and noone caught the difference. Anyhow, it means the same thing. Each time you drop a fow in melee, this value gets worse, up to a maximum of -5, then it stops.
Level difference grants higher BAB and MAB so that this will offset the No Prisoners penalty. In other words, using my 3 vrs 7 story above, assuming both at Cimmerian Barbarians with 16(+3)STR, the 3rd level guy at maximum No Prisoners penalty against him from the 7th (-5) would have a +1 to hit left down from +6 (STR+BAB for 3rd). The 7th level guy, on the other hand, would have a +5/+0 because he has two attacks and should normally be at +10/+5 (STR+BAB for 7th).
Flanking s a +2, so if the third gets into a flanking position against the 7th, the 3rd's attack goes up to +3. If he and 4 others surround the 7th, the penalty can go away entirely, adding to any Flank bonus that might exist (and should with that many guys ganging up). See page 177, Flanking, and page 187, Multiple Opponents (original printing).
I grant you, a WILL save might have been a more mechanical way to develop results, but they decided on the bookkeeping route. Plus, this feat is a follow-up from the Great Cleave feat and it lasts for the entire combat, not a round or number of rounds. The reason I mention that is that even opponents that can't reach or even see you will suffer this penalty once they get in range and with Great Cleave several opponents can be dropped all at once in a single round (basically).
I might have written that each time you drop more than one opponent in melee, all fore within LOS to you or any of your formerly threatend squares must make a WILL save minus the number you killed, max -5, or suffer a -2 on all actions that round that aren't focused on either staying still or moving away. It could even be that each time multiple opponents are slain in this way, all opponents must make a WILL save minus the slayer's character level for the remainder of the combat or they stop in thier track and run on a Critical Failure. Those might even be new Feats that I can isntitute.
Thing is, there's lots of ways around the -5 max penalty and I can't really see where the confusion lies.