Potted Magma Palm

This is not something you craft or buy. It comes out of the crates you pull from lava, so the route is a lava fishing setup and the gear that lets you fish there without losing the line. Work through a stack of obsidian crates or hellstone crates and the potted plants pile up fast enough that you will be looking for places to put them.

It puts out real light, enough to be the main source in a room, but the game refuses to count it toward a house's light requirement. An NPC room decorated with these still needs a torch or a lamp tucked in somewhere. There is no wiring hook either, so it burns from the moment you place it. The strange part is that a plant made of lava will happily sit underwater and keep glowing, which makes it one of the better options for lighting a flooded build.