Thorim 25-Man (and possibly 10 man too) Hard Mode Skill(s)

will be investigated and given follow up about this issue soon.

also, image link seems invalid. please provide one thats valid if possible in the comment.

https://imgur.com/NQc2AeZ
here is the screenshot from the 1st cast of thorim's CL

Cannot reproduce the chain lightning damage.

This chain lightning dmg were totaled from 3-4x cast. Hard mode triggered.
https://prnt.sc/2Dgl3rWVLrNm

Even after a long time too, the dmg did not reach 100K
https://prnt.sc/pI7AVahEXcUt

As for the ads, on the next update it is ensured that `Priests can MC a Dark Rune Warbringer.`

Then try to have 10 or 25 ppls on the fight. Maybe something messed up the chain lightning damage calculation. We notice the damage from CL not consistent at all. 1st pull we were safe from 1st CL damage but got half wiped by 2nd and 3rd CL (CL range across the map lol)

Before discussing this further, i would like to inform that if the Ulduar Instance is not recommended to be extended. From past player's experience, extending the ulduar instance will make some of the encounter anomaly.

Back to the topic. The Chain Lightning from Thorim does not even have specific scripting / damage calculation.
Also Chain Lightning will only trigger once its enter the ring.

https://github.com/azerothcore/azerothcore-wotlk/blob/master/src/server/scripts/Northrend/Ulduar/Ulduar/boss_thorim.cpp#L740

Have tried it multiple times with over 15 ppl (player+npc bot) with usual raiding positioning. Nothing unusual happened.

Even tried to take wipes too.

Some information i can get regarding Chain Lightning.

• Every succesfull bounce/jump, the damage will multiply from by 50% or 100% depends on difficulty.
• The bounce/jump is infinite target, means no maximum target and can be bounced within all players within the jump range.

Sources: https://youtu.be/Jhgm4tepLEQ?t=328 , https://www.icy-veins.com/wotlk-classic/thorim-encounter-guide-strategy-abilities-loot , and mentioned wiki.

For Chain Lightning spell description:

Difficulty 10: https://wowgaming.altervista.org/aowow/?spell=62131 

Difficulty 25: https://wowgaming.altervista.org/aowow/?spell=64390

Judging by the looks of your provided damage screenshot, its likely you got the final bounce effect or the bounce above 7.

Others:

Safe Chain Range:

https://prnt.sc/0gYL-WITKy67

Unsafe Chain Range:

https://prnt.sc/qZQ5ZF27a29F

https://prnt.sc/84IWxukiYlKn (This was 10y area, checked with /range 10 from DBM. The circle was colored red, not green.)

Dark Rune Warbringer's level was spoted at 83 and cap on level that priest is able to Mind Control is 82. It is now ensured that NPC is able to be Mind Controlled by Priest now.

Meanwhile as for the Chain Lightning still marked as Invalid. As cant reproduce while applying certain/usual raid positioning.

Some players receiving lot of damage from Chain Lightning.

There is no image provided that representing the visual example yet.

According to any open source emulation, CL does not have standalone spell scripting, and its fully depends on the DBC Files, which has been crosscheck amongst many DBC version and they are the same.

No idea what's the cause of this big sh*t damage, either from chained entirely, or the boss still got buff stuck (Enrage, etc).

More detail found about this specific encounter was: https://youtu.be/Jhgm4tepLEQ?t=363 . Informing the CL can jump infinitely. 

Will keep investigating this.

A temporary fix has been found, will be applied on next update.

The offset for CL jump will be made to 7 to 7.5y instead of 10y.

The Chain Lightning Jump Range were now made sure to not exceed 10y.

Additional 1y offset have been added. So the safe spot is 9y, but still 10y is preferable.