I started messing with the Mermaid Songs only to add one for the scared emotion... and ended up reworking them all...
They're very... lame in the game, and do nothing at all... SO...
1. I added the Kraken's Call, it will make the other sim very scared;

2. The Night’s Requiem have a stronger and longer effect;
3. Aegean's Question, instead of giving only a buff to make the sim tense, will actively sabotage them. While they have the buff, the sims chances of success in any interaction are lowered by -100, and skilling up will be harder;
4. Inspiring Berceuse, opposite of the one above;
Ok... here is the good one. I really didn't agree with this one at all...

Performing this one will apparently be the same as vanilla, but your mermaid... they will know something's different...

And it is.. the sim you performed the Song on is now under the mermaid control. And if they stay close to the mermaid, the power will reveal itself:

They get this buff from proximity, and when they have this buff on, they're fully under the mermaid control, and she can manipulate them:

You can ask various things, a special one is asking to swim:

Asking them to swim is potentially sending them to die, and happily, since swimming while under the effect of this command will sink their needs:

If the sim stay away from the mermaid, they'll lose the buff, and go back to normal, if they go in her presence again, they'll get the back the buff.
Stay away from your mermaid too long, and this will happen:

Once the sim is under a mermaid control, there is only one way to break the charming:

Getting a Soulmate relationship with someone will break the mermaid power (this also includes the mermaid who has the sim under control)

Also, a sim with a Soulmate will be immune to this power (they will only get the standard buff) and cannot be placed under control

And I decided to really be a dick about this, so, if you have read up to this point, get your reward here, because the file attached to this post is a dummy.
Deadly Duels and Vampire Deadly Duel are updated to include some interactions you can use in this mod.
UPDATES:
30/03
Fixed Command to Kiss not working
Zero_
2021-07-09 02:23:23 +0000 UTCLittleDevil-888
2021-07-08 22:48:38 +0000 UTCHissu
2021-02-27 10:09:47 +0000 UTCZero_
2021-02-27 00:31:44 +0000 UTCZero_
2021-02-27 00:26:45 +0000 UTCSweetLilja
2021-02-26 21:12:28 +0000 UTCicherelyn
2021-02-26 17:55:10 +0000 UTCWolff7676
2021-02-26 15:15:27 +0000 UTCKellie Schiavone
2021-02-26 12:38:26 +0000 UTCElunæ
2021-02-26 11:01:14 +0000 UTC