The black eye skull is missing from the vent. It should be in second vent at the beginning of the Library but its not there
Are you sure you haven’t collected it already yet? Once you access any of the terminals or skulls or audio logs they won’t pop up anymore in the campaign as long as you’re playing on that same gamer tag. Doesn’t matter if it’s a different playlist or whatnot, once it’s collected it’s collected.
I have it now the youtube vid I was watching did not mention it was past the big circle room I thought it was in vent at the start of level
Glad to see you got your issue sorted OP, feel free to open another thread if your require further help with anything