Ancient tablet pieces are needed for sub areas where you get unique items. There are two ancient tablet fragments in the missions; 1 in the mining facility and 1 at the miniknog stronghold. I'll be doing a run soon so you can see it in action.
The 1.4 update added a brand new boss and mission, accessible through your SAIL and unlockable through bounty hunting missions. It's necessary to add this to the Individual Level leaderboards here, so as of this post, please comment with your thoughts on the run and we should see some runs made of the level soon.
Personally, I think it's going to be the hardest boss to speedrun. This is going to be fun...
For the record, you do not need to run just what is on the Speedrun.com page. I have an admin% among my runs, and that's not being run here. Honestly, I'd love to see proof of concept. If you can record a run the way you describe here, I'm sure they will consider it.
By spamming thorn grenades before the boss begins attacking and getting it to 1/2 health, when it opens its cocoon it will spawn in the vulnerable phase. By then using thorn grenades at that stage, it's possible to kill it before it even has a chance to drop down. I estimate that this strategy can take 10-15 seconds off the world record.
With 1.4 out, a new mission involving mechs was added. I have a few questions with this in mind, does this make other AMM runs obsolete? Is there a speedrun planned for the mission itself or is it going to be a part of the rest of the missions? Should it be called main questline instead due to other main missions being given to you? (For example, Koichi's Museum and Vault quests) Is there going to be a separate AMM for all missions including Asra Nox post-ruin?