Y = the Baphomet (most particularly, for obvious reasons I hope), Satan, Lucifer, etc. All of these figures are associated with consciousness, enlightenment, illumination.
This image also contains symbolism re: dualism. The heavenly bodies; the right- and left-hand paths; as above, so below; male and female; human and animal; mortality and divinity.
Q has discussed the meaning of Y, in case you didn't know. But to be clear, I forget whether Y symbolizes what I said to the actual cult members or if the occult connection was invented by Q for the sake of simplicity.