Facilier's Shadow is the supporting antagonist in The Princess and the Frog.
As the shadow of Dr. Facilier, it is completely loyal to him, and serves as his inner darkness. Despite being somewhat one of Facilier's "Friends on the Other Side," it has no association with them, and especially fears the fate it and Facilier will face if he fails to pay back his debt. But when Tiana destroys his talisman, the voodoo doctor and his Shadow are dragged into the voodoo spirit world.
The Shadow could be interpreted as Dr. Facilier’s soul personified. The “friends” on the other side are actually the voodoo spirits or ancestral souls. When he made his pact with the voodoo spirits, he threw his own soul into the mix, thus separating it slightly from his physical body. Therefore when his Shadow is dragged down with the other ancestral souls, his body goes with it, because the Shadow is Dr. Facilier.