UPDATE 13/3/19: Developer Motion Twin has announced that Dead Cells' big free DLC update, known as Rise of the Giant, will be coming to PC on March 28th.
Rise of the Giant, which has been available to foolhardy beta branch testers on Steam for some time, introduces two new areas and bosses, ten new enemies, new skills and weapons, plus a new Skinning system, adding 50 outfits (including one that looks like Christmas tree for some reason) with which to adorn the game's flame-headed lead.
A more thorough round-up of Rise of the Giant's additions (plus some tasteful animated gifs) can be found on the DLC's newly launched Steam page.