This Easter Egg is on a structure 'guarded' by the raid boss Roaring Skylancer (passive). You can find it on top of a high, snow-capped mountain near Narsell Lake/Enchanted Valley - the coordinates are approximately 46.5 horizontal/40.5 vertical on your map. The mountain can be identified by a pathway spiralling around it up to the very top (which might take some looking for because of the size of said mountain).

The egg itself is on a monument at the very peak, next to Skylancer. It is covered with markings and several columns of letters with no apparent significance and no in-game NPCs or items make any references to it.

It is actually a list of the game creators' initials - in other words, congrats, you just found the credits. ;)