Walkthroughs for custom maps.

The author (Franz Liszt, also known as Louis Cyphre) used to upload videos of his playthroughs himself.

I sometimes watch his streams. In the third part of God Eater, there's an interesting mechanic that allows you to level up regular heroes to 6424 on the altar of sacrifices and in battles with ultra-legionary troops. But overall, the maps are quite easy to complete.