Going back to the pumpkin woods, I've done some analysis of the items you have to collect to lift this so-called "curse", even if it is the Flying Fortresses Protect spell. Here are the descriptions of the items:
1. Seed of Doubt: Was this really what you were looking for?
2. Last Straw: An extremely hard piece of straw! You can’t break it however you try.
3. Ghastly Veil: Touching this piece of cloth gives you a hollow sensation, like you’re disappearing!
4. Eternal Flame: A tiny piece of a very angry flame! How come your other stuff doesn’t burn up?
5. Root of Evil: A root with such bloodlust just looking at it sends chills down your spine.
1: Seed of Doubt
Ignoring the Pixel Ferrets' humor, this is dropped by a Jumpkin, the fast-moving and attack yet low health and easily stunned pumpkins. The seed part is obvious - it's a pumpkin, pumpkins have seeds. How doubt connects to this one I'm not sure, but what I am sure of is that someone will have some sort of idea, possibly to do with the "ancient magic" that brought them to life (quoted from the enemy codex description, I'll be doing that a lot).
2: Last Straw
Dropped by a Scarecrow. Described as being "extremely sturdy" and dropping a scarf that gives you extra defense, this straw seems to be connected to the scarecrows by their ability to take quite a beating. The "Last" part is, again, a little puzzling, maybe to do with the short straw? As in, bad luck?
3: Ghastly Veil
This is what we can assume as the sheet worn by or that is the main component of a Ghosty. The "hollow sensation, like you're disappearing" would reinforce that is more held up by something, either an invisible creature or magic, the latter seeming more appropriate.
4: Eternal Flame
I would assume this is kept inside a Lantern Jack's lantern, as no matter how long you keep one of the buggers alive, they always seem to be able to shoot at you. How come your other stuff doesn't burn up? It's not a hot flame, despite it's appearance being red which symbolises heat. This would also give us reason for why it doesn't set you on fire.
5: Root of Evil
The most powerful one of the five, it's dropped by a Halloweed, an evil mutation of a Bloomo. They're described as being "beautiful yet deadly", could be a reference to that part in the Bible where Satan, disguised as a woman, tries to seduce Jesus (don't quote me on that, I know my Bible as well as I know the lifespan of Faes). Although there's no seduction going on here. Also, they have an evil smell, as described on their petals, which would deter any passers-by. The root part - they're plants, plants have roots. Simply looking at a red root sends chills down your spine? Maybe then the root could mean a different thing...
Some final notes
A lot of the names have references to time - Seed and Root symbolising origin, Last showing the end and Eternal showing forever... seems a little odd if it's two dungeons later you discover time travel (yet to be added for anyone wondering) so maybe this has some sort of connection to that?
The first four are not enough to lift this "curse" by themselves, and need this "Root of Evil" to have enough power. This, combined with the "chills down your spine" and dropped by something which is an evil cousin of an angry flower, it could mean it is the origin of all evil... This could show the sheer power needed to lift the Flying Fortress' protection. And even though the bishop says the forest "cast this hex upon itself", why would he want to tell you? He doesn't tell you for what reason he wants to lift the curse, and he thinks you're just another ghost-in-the-making.
Finally, the altar is in a graveyard.
Something odd's going on here. I'm pretty sure something we haven't been told about yet.