1. What will happen to the region your family is from if it's island sinks.
I believe the old mechanic to deal with family homes on the old South Islands (sunk when Dwilight opened) is still around and will handle this.
2. Is immigration instant now and when the islands are sunk.
No. It takes time like usual. You need to do it yourself. For those who don't leave themsleves, later, the continents will be closed and there will be an 'emigrate' link from the Account page. In January, all remaining characters will be moved to another continent and the islands sunk.
3. What will these new realm be like? Its leaders, flag, and other things.
We've made various temporary adjustments to the realms that will be communicated to those players in the realms. Its leaders will be elected by the players in the realm. Flag and other things will be determined at that point and will be further communicated to the players in the realm.
4. Will we get notice when the realms are created.
Realms should be created by the time you arrive, in the next couple days.
5. Will we be able to takeover regions that are not next to our realm? So everyone gets a chance to make a realm on dwilight in the west.
This mechanic is not changing.
