Anyone know what or how Lunar Howl changes your werewolf?

It changes temperaments. They may even gain positive temperaments that reduce fury gain.

Exactly above, and in the description. Your temperaments are rerolled, which is basically a werewolf personality thing. Since it is a gamble, you need to be kind of careful, but not really since you can reroll again and again.

Yes, this can be done only once per night outdoors. No worries, as there's always tomorrow to try again.
If I guess it correctly, there are 6 positive temperaments that along with reducing fury gain will also slow down one of the needs. For example, mark of the moon slows down energy, mark of the hunt slows down hunger etc.
Sometimes one of the new negative temperaments might get replaced later on with a positive one. I had it happen as a negative temperament turned into mark of the forest (reduces fun gain).

kinda dislike that they're random; i'd prefer to be able to assign them to fit the sim's personality, the way you can choose vampire weaknesses.

"moon_moth;c-18132562" wrote:
kinda dislike that they're random; i'd prefer to be able to assign them to fit the sim's personality, the way you can choose vampire weaknesses.

This right here has me annoyed to almost anger. This is not the player's choice but a forced way to play how the devs want you to play with the werewolves. I am beginning to way more forced gameplay if you want to play a werewolf. I see fury building way to quickly even when you try to not to agitate those bad dog traits by no choice of the players. Sim wakes up and fury is like okay let's race to fill the fury ball as I said avoiding the bad dog traits.

I had a good, cheerful, and unflirty Sim.. All three temps went exactly opposite of those traits. So Sim was deleted because of the temps ruining not only the Sim, but her were form too. Sadly I am finding them poorer built (the lack of even a hint of weres being females), and way less Simmer friendly like the vampires.

I am hoping this horrible temp system gives the player a bit more control. If I want a cute uncontrolable (which still I get to pick their animal traits) animal ...... well there is the dog ...

It is possible to get four positive traits instead of the negative ones. I got it on my werewolf. It's basically random, but I did lunar howl up on the "hill" in Moonwood Mill. I tried lunar howl on different locations like the magic HQ, but ends up as random everywhere so that didn't matter.

I guess it could be that the more powerful you are as a werewolf, the more likely you are to get more positive traits when you lunar howl, but I can't confirm that in any way.

"moon_moth;c-18132897" wrote:
is there no cheat code available for assigning temperaments? if not i'm once again pinning my hopes on the modders

Temperaments work like traits, so those simple trait equipment and removal cheats work.
Thanks to the cheat list in this page, I can share the list of the temperament traits in-game:
https://ultimatesimsguides.com/sims-4-werewolves-cheats/

• trait_OccultWerewolf_Temperaments_AntiCapitalistCanine
  
• trait_OccultWerewolf_Temperaments_BigBadWolf
  
• trait_OccultWerewolf_Temperaments_Carnivore
  
• trait_OccultWerewolf_Temperaments_EasyExcitable
  
• trait_OccultWerewolf_Temperaments_FeelsOutcasted
  
• traits.equip_trait trait_OccultWerewolf_Temperaments_Frisky
  
• trait_OccultWerewolf_Temperaments_GrumpyWolf
  
• trait_OccultWerewolf_Temperaments_HatesBeingWet
  
• trait_OccultWerewolf_Temperaments_HungryLikeTheWolf
  
• trait_OccultWerewolf_Temperaments_Prideful
  
• trait_OccultWerewolf_Temperaments_RestlessAnimal
  
• trait_OccultWerewolf_Temperaments_SensitiveHearing
  
• trait_OccultWerewolf_Temperaments_SurvivalInstincts
  
• trait_OccultWerewolf_Temperaments_Territorial
  
• trait_OccultWerewolf_Temperaments_WolfBrain
  
• trait_OccultWerewolf_Temperaments_WrackedWithGuilt
  
• trait_OccultWerewolf_Temperaments_MustBeClean
  
• trait_OccultWerewolf_Temperaments_NightWolf
  
• trait_OccultWerewolf_Temperaments_Lunar_ForestMark
  
• trait_OccultWerewolf_Temperaments_Lunar_HuntMark
  
• trait_OccultWerewolf_Temperaments_Lunar_NightMark
  
• trait_OccultWerewolf_Temperaments_Lunar_WolfMark

The last four are positive temperaments.

oh man, thanks! i know just which ones will fit each of my sims

I did the lunar howl with Kristopher during the full moon thing, he got completely aggressive and I had to restart the game without saving. He lost his good temperament trait, and got territorial and hungry like the wolf, I didn't think it fit him well.

"crocobaura;c-18134652" wrote:
How many temperaments can they have at the same time?

Depends on the rank. First rank has one temperament, and each rank adds another one until the sim has 4. So 4 max.