Summoning Nightbane - Karazhan

[Vishax]

anyone knows how to summon Nightbane in Karazhan? i did some search and looks like the way you summon this boss changed many times between some patches, searched in wowhead and also did some search in some Romanian posts here, from the little i understood saw that it should be with a quest chain that starts with Medivh's Journal. however, when i take this quest it goes automatically as failed, tried with all my characters but its the same, and also tried going inside to turn it but didnt work.

any help would be appreciated