Chara was inside of the Void which is where They "Rest", due to the disturbance happening in the under ground, Chara has been awakened by it, opening his eyes with his left eye Corrupted and creepy and slowly went up to the surface and broke out from the ground with some void essence trail off of Chara, It appears that their body is glitching a little bit

"Who Dares to disturb this place?"