So each of the levels has a mid-Boss that shows up at the 10 minute mark and then a major boss that shows up at the 20 minute mark.
Defeating the second boss should drop a map that ends the level and unlocks the next level.
If that didn't happen, that's a bug that I have not seen. Maybe has something to do with leveling up with the exact same time is picking up the map and it overrid something but I'll have to look at that. Sorry about that.
As far as progression and unlocking characters, every level has a hidden character available to find in it. It has a chance to spawn as you move around the map, but it's not guaranteed every time you play. Your luck stat increases the chance of it. Spawning as well as increases the chance of things like crits and more experienced dropping from enemies and so on.
I do plan to eventually add an in-depth guide/ dictionary in the game to explain a lot of these nuances.
Unlockable character should have an outline like the elites and the bosses do. And after you defeat one they drop a crystal that unlocks that character when you pick it up.
Also each character has five talents that you spend the soulstones you earn at the end of the level to upgrade. Each character has a mastery skill which is unlocked by upgrading all five of their skills to make level. Some of the characters mastery unlocks a new character. Others add a new weapon to the pool or something.
So in general the gameplay loop is sort of designed to be:
Pick a character.
Play a level.
Try to find the hidden unlockable character by exploring more and more of the map and not just stay in one spot.
Defeat both bosses in that level to finish the level.
Spend soulstones on upgrades to eventually master the character.
Repeat in harder levels/ new characters/ the same level.
Currently besides the Knight, there are five other characters in the game. Mastering the characters to unlock some of them is meant to take some time/effort.
Thank you for your feedback and I'm sorry about the bug.
Hopefully that bug is so rare that you don't happen to get it again. Like I said I had not heard of it and not seen it myself but I will look into it.
I have a lot of changes planned for the presentation and some of the inner workings of the game. I just need more time to refine some things before I get the next release out.