Disco Ball

It hangs from the underside of a block, so you need a ceiling above the spot you want lit. The light pulses through the color spectrum instead of holding one hue, and it accepts wire, which makes it the easiest way to give a room a switchable party mode.

• It will not satisfy the lighting requirement for valid housing. An NPC room still needs a torch or a lamp.
• In a bright room the cycling barely registers. Put it somewhere dim or the effect is wasted.
• Rainbow Bricks run on the same clock, so a room built out of them swallows it entirely.

The Party Girl has a line about putting one up, but she does not sell them. The Merchant does, and only once your world has reached Hardmode.