Trion has added a new Nightmare Tide page to their main site. It doesn’t have any info yet currently, but it does have an animation where it shows off two Skelfs (new mobs) as well as an Akylios-like creature above.
You can check it out here.
There’s currently nothing else on the page, but it is likely that through the next few weeks we will see additional information start popping on up the page.
For those who can’t see the page, here’s what it looks like below:
RiftGrate 
I sense a high increase of Lovecraft coming later this year 😉