Anchor is a custom object that keeps a certain amount of chunks loaded around it. In those chunks mob spawning happens like there is a normal player located in the chunks.
In this guide we will analyze how to construct and place Anchors in your Realm.
To create an Anchor you need to construct a Level 4 beacon and on the top level place 9 Netherite Blocks instead of the material you used to construct the platform (check this reference photo). Then you need to place the beacon block on top and once it activates you have to right-click on it while holding a Totem of Undying.
The Anchor should activate. To confirm, around it, Totem of Undying particles should be falling from the sky.
Placing an Anchor in any location in the chunk doesn't guarantee that mob spawns will be efficient. We recommend to find an efficient spot by AFKing with your player first and then place the anchor on that location. Don't forget the Anchor behaves like there is a normal player in the world, so you should take into account how far the entities spawn and activate.
To delete an Anchor simply destroy the beacon block.