Light and Shadow is a Dark Brotherhood themed furnishing sometimes obtained from the Shadowy Supplier, Remains-Silent.
From the 2.7.3 Patch Notes
Fixed an issue where the flame for the "Light and Shadow" achievement furnishing was displaying incorrectly.
When I read that I thought maybe the Shadow/Void effect was only supposed to show when the Light was extinguished and was quite upset to see that it turned into just a skull with a candle on it!
I don't know if this is a bug or intended, but PLEASE bring back the Shadow!
"When the enemies begged for the mercy they lacked,
Three voices as one shouted "Blood for the Pact"
-excerpt from "Three Hearts as One" by Malukah