I think this is a bug

[dull pasture]

Korth passive and ultimate doesn't work with Premtsa specters which are defined as undead creatures

[granite knot]

Dear Traveller, Thank you for getting in touch with us and for sharing your concerns.
Regarding the ultimate issue, it would be highly appreciated if you send us the following details so we can investigate from our end:

• Role ID
• Video during the battle
  Thank you for your support and understanding.

[dull pasture]

ID : 2031693489423749120

In the video I use korth ultimate first on the specters which gave no buff and then I use it on his summons which gives the buff. Also his passive didn't trigger on the specters