Orb Celebi early on when it is flying around and then feed it an apple when under the log. Also look left while under the log and orb Serperior's tail (might hit the ceiling of the log so might need to orb multiple times). Orb Celebi while it is sitting on the Ruins. Lure Serperior towards the right. Celebration after eating is the high pose. Get Celebis in background by playing music at the group of 4 and bonk the Drampa in the back for more other.