I want to say I apologize for the super long suggestion post, I will probably make more posts here for new ideas if you want me to! Hope these ideas help!
Here is my best shot for ideas (may not be the best):
-More fight scenes in the arena:
1. Tentacle Monsters:
A. Much bigger:
-More cum
-Cum covering her body
B. More in scenes:
-Tentacle gang-bang
-More deep throating
C. More brutal?: (if that makes sense)
-Spanking while fucking?
-Tentacles moving through her ass and mouth then clumping up in her stomach?
2. Clan Mus'tah:
A. More black ooze tentacles in scenes
B. Futa opponents
C. Clan Mus'tah minions? They are like the breast sucking tentacles and do that same thing
D. Clan Mus'tah clone of Namu?
3. Zombies:
A. More powerful giant zombies:
-Deep throat
-Spanking?
-Stroke the cock with her breasts?
B. Futa zombies:
-Deep throat
-Spanking?
-Stroke the futa cock with her breasts?
C. Friends: (This is an iffy suggestion)
A. The ones control the arena and notice Namu's friends, so they make her fight them?
::Main Quest after The Undying King is defeated::
-Clan Mus'tah Invasion:
A. Kau'punki gets the first invasion while Namu and her friends are fighting The Undying King
B. When Namu and her friends get back Mainio is invaded
C. Kulma'la gets invaded as Namu and her friends go to save Mainio
D. Mainio is the first to be saved, then Kau'punki gets saved, and when heading towards Kulma'la, Namu and her friends stop by the Bewb-Tec Facility because Clan Mus'tah is trying to use the robots for aid in the invasion
E. After saving Kulma'la, the remaining inhabitants of the clan take Kiva back to their hide-out. They manage to cover Kiva in black ooze and use her against Namu and Purnima, basically like a boss fight. Once Corrupt Kiva is defeated, Clan Mus'tah stays in their hideout, and doesn't try another invasion? Until later...
F. The new leader of Clan Mus'tah sees the power in Namu and her friends and creates more brutal ooze monsters that can be used to destroy Namu and her friend's bodies?
-Zuhma'la:
A. A woman arrives from a land called Zuhma'la, a place mainly known for it's use of magic. She came for help because a futa witch has swarmed the land with magic monsters, tentacles, etc
B. When Namu and her friends arrive Namu comes to a small port town of Cital'a, which includes weapons, magic, and such like that to add more weapons in the future
C. From there the are four places, two towns, and one capital. Namu and her friends start in a town of Nula'tia. The magical monsters Namu and her friends face are just like the other monsters just more magical looking (if that makes sense)
D. Next, Namu and her friends go to another town of Tita'Muha, but each town they further go to, there are more monsters, and more brutal sex scenes
E. The capital is Wanda'kia, after saving them and defeating three magical bosses just like the zombie invasion of Mainio, you get support to head towards the Magical Forest where the witch resides. This is where the monsters get the most tough and fuck the three the most.
F. Once the witch is defeated there will be side missions able to be posted inside the city of Wanda'kia for Namu and her friends to explore?
I will make another post if you want of side missions for these two new quests and such! I again am sorry for the super long post XD hope these help give ideas!