Corruption Hole

Pass through the Lizard teleporter and go northeast until you find the part with Mutated Tigers, Mutated Bats and Death Blobs. Go up the stairs and you will find a Mutated Bat and a Mutated Tiger, go up the stairs again, go right and pass the building. You'll find wooden ramps, go down and follow the route through the place until you find a hidden hole. Go down, you will find some Lizard Legionnaires, Lizard High Guards, Lizard Dragon Priests and Lizard Chosens. Keep walking south until you find a ramp, go down there and you will be greeted by hordes of Lizard Chosens. At the northwest part of the cave are 4 Ghastly Dragons. If you have not handed at least 8 Tomes of Knowledge to Cael, you will not be able to enter the Corruption Hole.