"End Holdout" structure

On the sides of large End Islands you would be able to occasionally see the end of a Purpur tunnel sticking out into the void. This would be a series of floating chunks of Purpur solidifying near the wall of the End Island with strong wind currents stopping any attempt with an Elytra. After hopping from chunk to chunk, you would enter the new End Holdout, a complex of circular tunnels and round rooms reaching throughout the End Island.

Some of these rooms would include a lab with terrariums of Chorus Plants, a glass room staring off into the void, a nature preserve with bits of the Overworld to remind one of home, a testing room with an End Linkage that can teleport the user to other Linkages at any distance and cross dimensions (but cannot be moved otherwise), and a large vault.

This vault would be guarded by many a Cloaker: new variants of Shulkers that change their shell texture to match what a viewer would normally see if it wasn't there. Raiding Holdouts with a friend is recommended so one person can distract the Cloaker and the other can see through its disguise.

The loot itself inside would consist of piles of Plates of Ender: a new material that can be put onto Diamond tools (similar to Netherite) to create Tools of Ender. End Linkages would also require Plates as fuel to teleport between dimensions and move other mobs.

Overall, adding End Holdouts would give players a larger reason to visit the End other than the Elytra and be helpful no matter the stage of the Player.