Released in 2015, Castle in the Darkness wasn't the most talked about Metroidvania of that year (thanks, Ori and the Blind Forest and Axiom Verge) but I can confirm that it was very good, especially if the sprawling Wonder Boy games were your bag. So it's great news that it's getting an unlikely sequel.
Castle in the Darkness 2 is currently in development but it's anyone's guess when it'll release. It looks like it'll play similarly to the first, though the pixel art style wends closer to the 16-bit side of things, whereas the first wore an 8-bit outfit.
The first game was a solo effort by Matt Kapp, who has worked on art for games like The Binding of Isaac: Rebirth and 1001 Spikes. This time Kapp is collaborating with Simon Parzer and collectively their studio is called LABS Works. That studio is also working on Astalon: Tears of the Earth, which looks bloody amazing and not too dissimilar to Castle in the Darkness.
New mini-trailers for the sequel will roll out on the 2nd of every month apparently, so keep an eye out. In the meantime, here's the announcement trailer: