Oi, it is secret vore scene with that half-dragon thing. To get that scene, you must lose a fight and . . ehh . . You will get it :D
Viewing post in Anyone know how to get the last scene ?
open that door next to the shore escape (in the bottom left corner od the dungeon, using the lockpick is fine, if you don't want to get the key from the bathhouse moles in the right room), turn the valve in that room, and escape from the shore, the dragon is an optional fight there in that hidden section, hard to miss though, just go straight.