Unofficial Skyrim Special Edition Patch

Spells which NPCs use, such as frostbite use the slow:speedmult.
Effects using this associated item include FrostSlowConcAimed (B729D)
FrostSlowFFaimed (B729F)
FrostSlowFFContact (B72A0)
FrostSlowFFselfArea100 (B72A1)

The issue occurred on a save which only used the unofficial patch and the following mods:
'UNP female body renewal', 'Less aggressive animals', 'a quality world map', 'enchant and smithing potion duration' plus a personal armour mod that I was testing. I can see no edits to spells using the slow:speedmult effect. Mine certainly doesn't edit the vanilla forms, though as described later, I do edit my own duplicated version of the form in order to obtain a specific desired effect.

This save has not seen any other mods and my masters have been cleaned. DG has been cleaned twice and also manually cleaned. All following procedures outlined on Nexus.

The issue is that this effect works on the player, but fails to work when the player uses the same effects on NPC actors.

My evidence for this is simply based on testing.

While enemy NPC frost spells can and do slow my movement, no amount of using the frostbite spell on any enemy ever succeeded in doing the same.

Sufficient frost and magic resistance does seem to allay the player being slowed, so there must be some mechanism that I haven't found that is deciding in the game when to apply it.

I've read that your stamina has to be at a certain level before the slow effect is applied. if so, this is deep in the game engine somewhere, because the slow magic effect is not conditioned this way, nor are any of the instances where it is used in the spells themselves. * see footnote.

If there is a link to low stamina, then my testing should have produced the effect on most of the actors tested. I chose Torvald's cave, full of falmer. I killed them all using frostbite (novice difficulty). Until they entered bleedout or died, none of them slowed down at all. Since the Falmer tested have significantly higher health than stamina (nightprowler04Boss 640 health, 357 stamina for example) and frostbite is a dual value archetype with 2nd av weight 1, it follows that the stamina of the falmer would have been exhausted when their health was around 45%. I also tested at Fellglow Keep to give ice mages a chance to slow me and to see if I could slow them. Neither happened, but I had 80% frost resistance and around 50% magic resistance. I also had high stamina (320) and the 'Wind-Walker' perk active, so my stamina was not being badly damaged at all. None of the mages were slowed even to the point of entering bleedout. This does show that there is a calculation/condition being applied somewhere because my character is definitely slowed earlier in the game. I could test a lower level save and check this again. It also seems to back up my claim that NPC actors are never affected by the multiplier in the magic effect.

I found this issue due to wanting to add a unique weapon with health damage and slow, which was conditioned to act only on Dwarven actors (and could not be disenchanted). The enchantment and effects used were all new forms to avoid editing vanilla forms.

The health damage (effect 0) worked exactly as intended. The Slow (effect 1) only appeared to work once in several dozen attempts. When I added a script to the effect which basically added 0.1 inventory weight to the target on effect start and removed the same amount on effect finished, it worked perfectly, as intended.

Then it worked and slowed the dwarven actors, for the specified time, confirming reports that I'd read that the slow effect works on NPC actors if their inventory weight is altered at the same time as the effect is being applied.

Other reports that the effect will work if the target is drawing or sheathing a weapon, I cannot verify, except for that one instance, when I shot a dwarven sphere just as it transitioned from not detecting the player to detection. At this point it was arming itself. It drove me crazy trying to replicate it but I failed every time. Is that the same as un-sheathing a weapon? I don't know.

The description of these spells that the player sees makes no mention of a slow effect, only the damage to health and stamina but I do not take this as proof that Bethesda did not want this effect to work, even if it is somehow dependent on other factors, such as stamina level (which I have disproven for NPC actors). These are hand-written descriptions that also neglect to mention third effects such as the paralysis which can take place with the perk PerkDeepFreezeParalysisConcAimed. It may be that Bethesda initially wanted the slow effect to be applied and later changed their minds, or it could be that they genuinely didn't want it to work for the player.

That last paragraph is naturally my opinion and not any proof that it is meant to work for player spells and enchantments, however I wonder if you would consider this issue and decide whether or not it is a matter for the unofficial patch.

I marked the 'bug' as very low priority simply because I've played thousands of hours and not ever thought about this. Others have, though. There are plenty of threads around with people asking about it, not least since it is a quoted effect on the Elder Scrolls Wiki pages.

Personally, I think it would be OP if implemented on every frost spell/enchantment, right from the onset of the magic effect, but if it could be linked to low stamina or some other actor value, then it would be a welcome addition for mages.

Thanks for reading this.

Footnote: if it is deep in the game engine there may be no way of altering it. I'm hoping it's just that I couldn't trace it.