Your first step needs to be positively identifying the last quest you did in Vol 1 epic. Compare your completed quests in your quest log to lotro-wiki's Epic Quests overview; you may want to start at the Vol1.Book8 list.
Ignore the instance quests in your completed quest log; focus on the chapter quests. What was the last completed book chapter? Are you currently on a book quest, and if so, which one? If you can answer those questions, we'll be able to help you much more directly.
Note that lotro-wiki's pages do not mention a "Mordirith's Bane", but "Mordirith's Fall" is Vol1.Bk8.Ch5. If you've completed this and also completed Vol1.Bk8.Ch6, you're done with Book 8 already. Have you completed any of Book 9?
Unfortunately you can only get in-game assistance from a GM by submitting a ticket in-game. You could try submitting an account ticket at https://myaccount.turbine.com/, or you could purchase something to make your account Premium or VIP and thus eligible for in-game help.
Originally Posted by Brodrick
Join the LotRO Volunteer QA Team!
Use the [url="http://lotrobugs.turbine.com"][color=red]bug reporting tool[/color][/url] or type /bug in-game!*
[SIZE=1]*no rants please[/size]