This concept is pretty old and it's been on my PC for a long time. I never published it because its lore felt not good enough - I changed it milions of times, trying to tie this champion - or currently just kit - either to my long-forgotten Project: Fyrone, or to Hirana Monastery. In order to be able to think clearly, I need to get this kit off my head and the only way to do so is to publish it. With or without a lore and personality. Pure kit.
While this concept started as a rework for Old Karma, I quickly replaced almost all and then all of her abilities. Then she lost her personality and somehow - I scrapped the rework and started a new champion, whose first and perfect, I believe, use is to punish enemy casters - even those who build AD. Nahtan - because this was supposed to be his name - is an assassin or maybe fighter or maybe even something else () meant to survive enemy casters' combos and then get rid of them, preferably not far from main teamfight (Gold and worse players will understand this better than any other...).
His skills are also quite good in laning phase and can set up ganks for his jungler, and let him survive and disengage from enemy ganks if used properly. RIP interpunction.
Nahtan, Custodian of Hiranian Library, uses something between "Old Mantra kit archetype" and "New Mantra kit archetype". His ultimate is automatically learned at level 1, and it can be upgraded at levels 6, 11 and 16. It is used to empower his basic abilities.
Edit: Thanks for suggestions and errors pointed out in the comments. I updated the post with them in mind.