Into the Darkness is a single-player dark-fantasy roguelite deckbuilder. Players choose a hero, build a deck, equip weapons and relics, and plan routes through expeditions featuring turn-based card battles, bosses, and events. Between expeditions, players return to the Lantern Yard to manage their collection, craft equipment and potions, and develop talents and guild progression. Each hero has distinct cards and mechanics that support different combat strategies.