Eye Of the Storm Temple
0. Entrance. There is a sea shore with partially stone floor, 4-5 rust devils represent welcoming party. They are here to guard temple from ocassionally attacking water elementals from the ocean (result of weird magic dissonance of controlling the Storm via temple).

From entrance, there are 3 paths:

1. Main pathway to the heart of the Temple. This is a corridor to the Boss Fight. However, it is closed via undestructible Force fields with Prismatic walls and cannot be teleported through. But, it can be opened by powering down two sources of energy in nearby paths - this is visible via detect magic.

2. Path to Apostate devil. In this room, Apostate devil is meditating and serves as energy source to the Main Pathway (see 1). He is bored - contract makes him bound to this place and he cannot leave by his own will, but if PCs converse with him, he can agree to be banished from this plane. Additionally, he can give advice about the Boss for money (few thousands of gold per advice). But initially he is so bored and starts to fight, and when he is losing, he can negotiate (for banishment or other things)
2.1 Lemur's Room. After the devil's room, there is a room full of lemurs. Their part of the room is separated from PCs by the lattice. Lemurs are used as a source material to create new devils by the Boss. In this room, there is a teleportation circle which teleports lemurs to the Boss so he can make more devils if there is shortage. However, to activate this circle, special key is needed from 3.1. This teleport can be used to surprise the Boss. Apostate devil can advise to use teleportation circle in this way.

3. Path to prisoners. In this room, there are halfling prisoners. They are used by Handmaiden devils for sacrifices to power prismatic/force walls. Prisoners can tell that devils periodically take some people to 3.1, and also sometimes devils just pass through this room, after that new devils appear (actually Handmaiden devils go to 2.1, unlock lemurs and the teleport circle and then Boss creates new devils).
3.1 Room for sacrifices. Contains machines in which neardeath halflings are drained from life power. 4 Handmaiden devils located here attack anyone who is not devil. Handmaiden devils possess magic key to unlock teleport in 2.1. Liberating or killing halflings will result in disturbing prismatic/force wall.

4. Boss room. There is a Pit Fiend as a Boss. One or two (depending on the party level and size) Advodaza devils also here.
To get here, entrance wall should be disabled via destroying/banishing Apostate devil(2) AND disturbing halfling energy flow (3.1).
Alternatively, teleport circle can be used to distract Pit Fiend. Once lemurs appears, he starts to mend some new devils from them, and will be distracted. If PCs use this approach, they can get a surprise round. If they will wait too long, then a new devil may appear).

After killing Pit Fiend, central altar can be used to stop Storm from gathering - this will require using the Hurricane Crown.
Pit Fiend can also be satisfied if PCs give him the Hurricane Crown. This will free Druvalia's soul (if there is some interest). But in this case, there can be some possible problems with Ruling of Shackles (King or Queen without a Crown???).

Ask questions, if you have any.
If you will play with these ideas, I'd be happy if you post how things go in your case.