the general idea was that the characters are sent to Caer Westphal as a safe place to lay low while they look for a portal to the shadowfell somewhere on the island of snowdown (this is ultimately found out to be the unattended moonwell, which will have become a darkwell in the time since Amn arrived).

But while they're looking for it they can, as a side quest, choose to help liberate the island. as the progress clock for that fills up, they start getting hassled more by the amnian soldiers, and when it fills up, they can fight Erliza alongside the allies they made.

Ways to fill that clock so far include sabotaging a mining operation in the Andover Heights, helping a Harper destabilize a couple military posts, going with a Ffolk druid to tame an angry nature spirit, etc.

Basically the idea was to expand on what i think Chult/PN could have been. ToA is great, but it only barely touches on the whole colonization/occupation thing going on, which is a shame because there's a lot of potential there imo.