The quest that opens up the Sewer teleports is "
Disappearing Soldiers". Once you can accept that and have it in your log, the teleporters will appear. If abandoned, they will disappear until it is picked up again. Once handed in, they will be there permanently.
However, the list of missing titles indicates that you are missing the entire "Lionheart Knight" quest chain in the zone.
When Mark Ferrero appears in the Pig in a Pond pub, he gave you a quest to retrieve his goods from the Mallen Bandits. as that quest completes, Kai Kaiyinth should have appeared nearby
asking you to visit him in Dalanis. Try finding him and seeing if he gives you a quest. He will probably be near the big boulder near Sunset Mirror Falls.
If you've already completed some of the quests that Kai Kaiyinth gives, it's also possible that you may have missed a cutscene near one of the trees south of Sternhorn. When you hand in a
quest to him there,
Betty Ilun will spawn and Kai will ask you to
take care of her. Eventually, she asks Kai to retrieve her son from the Mallen Bandit gang.