Phase 8 of SoD introduces an entire new neutral town called New Avalon, extending out from Tyr's Hand. This town is home to Phase 8's raid, Scarlet Enclave.
In order to gain access to the town, there is a short attunement questline. Being attuned to Naxxramas is a requirement in order to gain access to New Avalon's attunement questline. It is not currently known if the town's attunement is required for access to the Scarlet Enclave raid, as it seems the Scarlet Enclave instance portal is located in front of the town. Only time will tell.
Before continuing with this guide, be sure to update Questie - it will help a lot. The majority of Wowhead's data is currently missing or inaccurate regarding this content. Questie has been updated for P8 as of v10.19.2.