Ocean Cage Challenge

this can be applied to an existing game and it should work fine.

This adds a layer at level 16 that requires level 45.  these entities will teleport you down 5 blocks if you get within 5 blocks and don't have the level requirement.

That may seem a bit artificial but it's done to make the fastest path out less clear. yes you can grind out xp. but it might be worth it to pursue going around the layer with a nether portal (if you can get a diamond pick) or maybe make a village. at any rate it makes the playing for time path less clear.