The Hallows Bane seasonal event has begun, and will last until the end of October 31st.

The 'Litheor' mission chain has been completely archived for ranks 100+. This includes the following missions:

Tremors From Below
The Litheor Egress
The Message Within
Uncomfortable Diplomacy
Silent Extraction
Reaching the Core
The Isolation Factor (new)
?

As usual, the missions must now be done in that order - so you will likely need to complete some of the earlier parts if you started later.
Unlike previous chains, this one has a 2-part ending. The final mission in the chain (as well as its associated medal) will be released soon. Good luck!