Here is what i found so far after wearing this Necklace around Den and the Temple...
• It does not force a Tonberry to use an ability more than another one.
• It does not make you get no aggro in Den nor the Temple.
• It does not save you from building hate upon killing a Tonberry.
• It does not make Throat Stab miss all the time.
So far, i only found one concrete thing, which in my opinion is worthless. When getting hit by Everyone's Grudge/Rancor, you get the full effect of the ability plus your TP is reduced to 0 before you technically take the damage from it, which means you will have 2% TP.
Other things i noticed...
I couldn't get Words of Bane to not miss me since i got the Necklace (always wearing it once entering Den or the Temple). Thought i wont say it makes Words of Bane miss all the time simply because we all know it isn't a very accurate ability. (I am 75 NIN so i evade quite a lot)
Right now, i tried to evade a possible Throat Stab but it was an Everyone's Grudge. I was already running to avoid so i was facing the other way and a little out of range of regular hits. The Tonberry right before that one hit me with Everyone's Grudge for 134 damages and as expected i was down to 2% TP. But for that one i took 30ish and was down to 1% TP. This was the first time it happend, also the first time i was facing the other way while taking a Grudge. So maybe there's a story about distance, facing other way or running while Grudge or Rancor are used on you while wearing the Necklace.
[Edit]The Necklace drains your TP to lower the damages from Everyone's Grudge/Rancor depending on your TP and your Tonberry hate.
Edited, Sun Apr 9 05:54:13 2006