You unlock the crusade spells in certain "dungeon" type quests. You unlock most of them on one and the last four on another one later on. This quests do NOT appear if you didn't get the achievement in Crusade.
Hey, I know the developer cared at least a little bit about this because they had a proofreader on the credits, so: I found a grammar mistake, if you choose to nuke the Ahopalooses, one of the dialogs is: "... and I'm you're human wh*re", it should be "your" instead of "you're".
To those that can't double jump (@Corloc): The double jump is not an innate ability, but a power up, which means: You can't double jump unless you have feathers. How do you get feathers? By grabbing flowers and given them to Souly, the girl.
I found an exploit so you never die and lose your progress. If you ever start fighting an anemy and you know you're not gonna beat him, quickly press the item button, it will pause the battle. Now click the little metal thingy under the loot button, it will bring up the options menu. Now click "Exit to Title" and tadaa! You will be back at the title screen. When you load your save you will be at the beginning of the last floor you visited, now you can escape or plan a better strategy! (+ to keep alive)
To everyone complaining that the save function doesn't actually save, the game only permanently saves at the town, if you enter the cave with floor 10 checkpoint unlocked, save at floor 60 and then die at 61, you will have to start again at floor 10, because of 2 reasons: 1.- So you don't abuse the save feature and make the game too easy, and 2.- Because if the save was permanent you could save with 10 hp and no wings, which would make the game unwinnable.
Thanks for the heads up!