Level Requirements.

Here is a list of the level requirements needed to enter restricted maps, thanks to Joey for creating the list.

To Aeven - 5
To Biters - 16
To Port - 6
To New Swamp - 12
To Desert Pot Shop - 6
To Desert (Gnomes, Rocks, Goloms) - 14
To road to Castle - 8
To Castle - 8 via the main road, 7 (take the secret route in Peri Peri farms)
To Hallowdale - 8
To Ants - 8
To Labyrinth - 8
To Outlands - 10
To Sepul - 10 via Outlands path, 15 via Anundo/Forks path
To Beast - 10
To Donom - 10
To Alex Borg - 10
To Proto 2.0 - 10
To Malone Outlet - 7
To Gameroom - 9 (even though guard says level 10 entrance)
To Centaur - 11
To Stronghold - 7
To Death Cave - 7
To Haunted House (all floors) - 7
To Anundo - 7
To Forks - 7
To Rabithers - 15
To Bahamut's Lair - 35