Sandworm

The giant sandworm easter egg can be found on the halo 5 multiplayer level The Rig.

You will need to do certain actions before activating the easter egg.

Activating the easter egg
To start the sequence you must first use your ground pound ability on a circular platform at the open deck area. You will know if you have done this correctly as the platform will buckle and break.

The next thing you will need to do is destroy two power cores using any weapon, the first is located on the back rail and the second is located just ahead of it at the Yellow corner. ( Destroy the yellow corner core last ).

After destroying the yellow corner core look slightly to the right and you will see a large mining vehicle be risen up, crushed and swallowed by the sandworm itself.

Trivia

 * This easter egg is a reference to the Dune movie and how the sandworms attack their prey, by rising from under the target and crushing it with its powerful jaws before returning below ground.