After Chara leaves, you see what appears to be a transparent floating head with a rainbow coloured scarf, the head resembled that of Asriel's former body, he also had 2 floating hands, his eyes were pure black with red slits as pupils, and his mouth was filled with a black, liquid substance that slowly dripped onto the floor, his mouth moves, but no noise comes from him, however you begin to hear his voice echo in your mind

"so...you survived Chara, she'll be back, don't worry."