Re-Logic and Engine Software have announced Terraria: Otherworld, a new Terraria game set in an alternate universe.
Here is their description of the game from the official forums:
Set in an alternate dimension within the Terraria universe, Terraria: Otherworld places the player in a life-and-death struggle to restore a once-pristine world – now overrun by a malevolent force that has corrupted nature itself – to its original splendor. Along with a rag-tag band of survivors, will you be able to successfully harness the power of an array of weaponry, magic, defenses, and even the world itself to thwart the designs of this unseen evil?
It will still be a sandbox game with role playing and strategy elements, but apparently there will be a change in core mechanics as well.
As they have clarified, the game is not a sequel.
We don’t know much more beyond this, although you can watch the announce trailer below.