Hello! As stated earlier, the only place enemies respawn are faction prisons, and boss floors can spawn prisons. For example, Fuuka will drag you into the shiny new Witches' Coven prison that spawns on her floor if she defeats you. Except, the thing about respawning only in prisons is not really true. Time and time again I noticed that enemies can respawn on the main floor, coming out of faction prison enteraces. And, when you go back and forth between floors, main and jail alike, sometimes, enemies spawn next to you. Most of the time they have 0 HP and disappear even if you don't hit them in the next turn, but sometimes... well, let's just say, going between floors while you are tied up tight carries a certain risk with it.
Now, two tips for breaking allies out of prison:
-You can tell your ally to stay right where they are after you freed them. Then, they won't follow you, and provided that you carve a way through the enemies all the way to the exit, they are unlikely to be found. When you get back to the main floor, the freed ally will appear next to you.
-You can use the Light Orb (or whatever the name) spell to place a light orb right on top of the enterace of the faction jail. It will stop respawning enemies altogether. Just be careful, the light orb can and will shoot at enemies in its line of sight, and they might aggro on it and destroy it in turn. For this reason it is not suitable for stealth, but if you intend to clean house, it will suffice. When you want to exit the jail, attacking the light orb yourself will make it disappear instantly, allowing you to pass. Other barricade type spells might work the same way, but IDK, I didn't test them.