Currently, this is how the set is according to the UESP which is 100% accurate. (unofficial elder scrolls pages.)

1 item: Adds 14-1206 Maximum Health
2 items: When you deal direct damage, you have a 10% chance to summon a Lich crystal that explodes after 2 seconds, dealing 102-8800 Magic damage to all enemies within 4 meters. This effect can occur once every 3 seconds.

But I am pretty sure, much like many others who know, there is just a slight hitch, one which I discovered recently and not quite sure if it is intended, but, when dealing somewhat direct damage with abilities such as liquid lightning or elemental blockade, it does not proc, the only time it ever procs, is when I use a light attack with my lightning staff (or inferno stave as I tested this with my sorcerer.) but interestingly, this also brings up another thing to mind in regards to the Valkyn Skoria monster set, when said damage from liquid lightning and elemental blockade is dealt to enemies, it actually procs Valkyn skoria even though the Damage numbers are not considered a Damage over time (because figuratively, Damage over time numbers are indicated in orange and come from damage sources such as soul trap, lightning staff heavy attacks, etc. whereas damage from liquid lightning and elemental blockade on the other hand, deal direct damage as indicated by the white numbers that tick. And in this instance, Nerien’eth is supposed to proc from the direct damage dealt by liquid lightning and elemental blockade, but it does not sadly, whereas valkyn skoria is actually proccing from the direct damage done by liquid lightning and elemental blockade.

I can only assume several theories.

1. The damage from elemental blockade and liquid lightning are somehow topsy turvy and proccing valkyn skoria with direct damage and not nerien’eth.
2. The Damage done by moves mentioned above are not as they seem and need to be patched up.
3. The damage proc mechanics mentioned in both sets need to be looked into and properly organised in order to proc properly in accordance to the respective damage done.
4. I may be missing something crucial in the Damage mechanics.

Because let’s be honest here, isn’t it a bit redundant that Nerien’eth is a monster set that deals magic damage and that it is not working properly for sorcerer builds?
Personally, Here is where the idea “may” fix the problem I speak of.

Nerien’eth set
1 item: Adds 14-1206 Maximum Health
2 items: When you deal elemental* damage, you have a 10% chance to summon a Lich crystal that explodes after 2 seconds, dealing 102-8800 Magic damage to all enemies within 4 meters. This effect can occur once every 3 seconds.

(*Elemental damage that consists of either Magic, frost, shock, flame or oblivion damage.)
This may help slightly, but really, the Nerien’eth set should primarily work properly with sorcerers and other characters sporting a stave so to speak. most importantly, heres an idea on how the nerien’eth set could be improved.

1 item: Adds 14-1206 Maximum Health
2 items: When you deal elemental* damage, you have a 10% chance to summon a Lich crystal that explodes after 2 seconds, dealing 102-8800* Magic damage to all enemies within 10 meters and stunning them for 2 seconds. This effect can occur once every 5 seconds.
(*I strongly suggest reducing its overall damage by 15-20% or more to compensate for the added 2 second stun lock and increased explosion radius.)

I just thought i’d Speak my mind and provide some feedback/ideas.
@ZOS_RichLambert