and where do you find that??? I'm so stupid I can't find it
You need to finish the lizard questline first. Then you have to look through the dark swamp until the character from ToS appears. When he appears you will be in a new area called ''Misty Abyss''. Then he will show up at the lizard's temple with his questline. (I don't want to spoil anything - personally I think it's well written and worth to go through)