Furniture2,537

Before an NPC moves in, the room needs enough enclosed space, background walls, a door, a light source, a flat surface item and a comfort item. That last pair is where people get stuck: a table and chair are the cheap answer, but any piece the game files as flat-surface or as seating counts, which is why a workbench and a bed can carry a room. Beds do more than that. In a room that also qualifies as a bedroom they set your spawn point, and separately they let you sleep, which runs the clock five times faster.

A few items here change how the game behaves around them. Water Candles push enemy spawn rates up and Peace Candles pull them down, both when placed and when held, and holding one while another is placed stacks the effect. Regeneration across an arena comes from the Heart Lantern, with the Star in a Bottle doing the same for mana. Statues wire up to spawn enemies or critters on a timer. Monoliths change nothing but the screen.