The Shores of Taishi DLC features a brand new island type (the Celestial Shores) with new tile types, items, locations, enemies, recruitable characters and more. Once the DLC is activated it will expand possibilities across the entire game, both in Campaign Mode and Director Mode.
Full feature list:
New island type: Celestial Shores, with a completely new set of tiles, a new game mechanic related to teleporting between islets and the new Peacock Tribe
6 new Recruitable characters: Red Panda, Tanuki, Ghost Catcher, Warrior Peacock, Shaman Peacock, Scout Peacock