Make sure to check changelogs for any new changes!
Contained Niko is a light source seen in the Progressiverooms, but is rather rare of its use.
It is a small, orange bucket with a pumpkin carving-esque face on the front. Inside, and "contained" is a feline-like anthropomorphic plush, known in the real world as Niko. A lightbulb comes with the item and is crucial in order for it to work.
With the lightbulb in one hand and the bucket in the other, the lightbulb plush will glow and light what is in front. This will not work if said items are more than a mile apart.