Ah, ok, I didn't have that info on von Kharkov, I guess. I like the trance ability, too, but I think I'd leave off the telepathic command schtick. That can be the vampirism coming through.
OK, then, here's a draft:
Thrall Bond (Su): A panther lord has a permanent telepathic bond (as the spell, except it can't be dispelled) to all the werepanther thralls it creates. Note that the thralls are only bonded to the lord, not to each other. If a panther lord is killed, all the werepanther thralls it has created immediately fall unconscious, undergoing a magical shock that transforms them back into the people they were before becoming werepanther thralls.
I wanted to use a condition defined in the SRD. Besides, only the Dungeon version has convulsions. The MCA2 version just says, "Upon the death of the panther lord, all werepanthers of the tribe permanently revert to their human form." That gives us whatever leeway we like. But I think the main thing is to keep the reverting thrall incapacitated. Do you prefer something like stunned or staggered?
What about using dominate person as the basis for the bond?
I guess I'd go with stunned, in that case. And I can go with charmed/dominated. Here's a draft:
Thrall Bond (Su): A werepanther thrall is permanently charmed (as the charm monster spell) by the panther lord that created it. If the panther lord spends XX rounds concentrating on one of its werepanther thralls, the panther lord is able to dominate the thrall (as the spell) for the duration of concentration. If a panther lord is killed, all the werepanther thralls it has created immediately become stunned for XX hours (no save), undergoing a magical shock that transforms them back into the people they were before becoming werepanther thralls.
There are a couple of things to figure out, but how's that for the basic framework?
That works for me!