Alwa's Legacy on Steam: https://store.steampowered.com/app/1205900
Bosses in video:
[00:00] 1. Imprisoned King
[01:14] 2. Sir Pent
[02:29] 3. Desmond Grim
[04:28] 4. Queen Eydie
[06:09] 5. The Architect
[08:08] 6. The Collector
[10:12] 7. Protectors of the Realm
[12:14] 8. Vicar
Not a bad metroidvania, even if the bosses were simple and easy. But final boss sucks. It's a copy of a previous fight, and then the second phase ends before you realize it.
There's also another game in the series, but I don't know if it's worth playing.