Brainwashing

 You take the necklace and incantate olds and powerfull words of enslavering . The target need to make an Intelligence saving throws or being Charmed by you . When it's charmed in this way, it cannot perceive anything other than you and is neutralised . When the target it's neutralised, you can described to they their behaviours and believes on something . That can be a general decription, like "From now, the only thing you love is to serve me ." or a very specific behaviour like "You admit that the one you is in love with is just a friend ."

This spell don't put the creature under your control, but it can be used to make it help you . Also, this spell don't change the memories of the target but can change they feelings and emotions . 

If the target live or see an event who can make it doubt about it's behaviour, like if you kill one of your servant in front of a target you used the spell to make it obey you, the target can make another saving throws . If it suceed, the spell is dispell .