So I did found out a pretty nice place to level up. As I matter it is the very same place I used the last time I played the game! There is this room at the last level of Dungeon Wrong with an upward stairs, and exit to each side and four big sort of pillars to each corners.
As it turns out, each of the pillars contains three deamons, which are amongst the most rewarding monsters to kill in the same as they give a big whooping 19 XP each time. Which makes it 12 deamons, altough to actually grind you need to only kill 11 each as monsters do not reappear in room and you kill them all.
The technique is simple. First you need the crown of Lord British equipped so that the deamons can not possess your characters or teleport outside of the pillars. Then you need to equipe your characters with either a morning star or better a Halberd which allows to attack two tiles away. This way you can go an kill these deamons over and over again without any risk of damage.
It just takes a LONG time.
So having now my Avatar at Level 6 and my other PCs at Level 5 I’ve decided to go and try to free Lord British with them. It’s probably gonna be hard, but there’s a chance it might be doable…