Thanks for the clarifications guys, I knew the DM was missing something when he pulled this encounter on us. I DM quite a bit for our group too, but I've never used harpies before so was unfamiliar.

Here in lies the problem with the way the other guy was using them. Once a character had failed his save the DM insisted that the harpies could continue singing even while attacking the character that now had to stand there and not resist it's attacks. I insisted there had to be another save allowed at some point or the harpies CR rating just didn't make any sense.

Using his way it seemed very unlikely that any character would pass all eight saves in a row and thus the probability of total group annihilation was way too high.

Glad to hear that the special ability replaces attacks like I thought it should and a new save will be allowed after the harpys free attack round. That makes a lot more sense to me.

Now here's another question.... what do you think the harpies CR would be if in fact it could continue singing it's captivating song at the same time as it takes it's free attacks. I'm thinking it would nearly double it since it makes a group of them become a lot more deadly. In fact I think they'd be almost broken if that were the case.

"Save or die" was the way I was looking at it at the time.

The major problem I see with the hypothetical "what if they could sing and attack" is that harpies come in groups and should the group be large enough... sooner or later if you force PC's to make enough saves, odds are everyone will roll a 3 or under on one of them. Especially if it's a group of 8 harpies.

I don't really see what the need would be for harpies to have high HP. Their song is effective from 300 ft away, line of sight isn't even required, and they can fly to boot. I think it's safe to say that if they could attack and sing they would just make sure the opponent is captivated and then safely swoop in for the kill, no matter how long it takes them to roll enough natural 20's.

Reguardless, they can't sing and attack at the same time, a new save is required after the free attack round and once saved the character is immune for 24 hours. So it's all good... so what if one or two harpies gets a free attack or two at low attack bonuses on the PC's they get to save again... more than likely become immune and then the harpies will be forced to retreat or they're the ones in trouble.

Once again thanks for the clarifications guys.

I'll have to set the guy DMing staight on this topic next time I see him.

Not sure he'll be receptive to it though. When I looked up the rules and showed him that special abilities replace attacks, he just turned to me and said: "Well these ones don't!"

Very frustrating when as a PC you recognize a save or die situation has been created by the DM weather he realizes it or not, and he's already told you that they're still only going to be CR 4 creatures.