This was moved from the top post, because it was getting too long to edit: The Beholder Anti Magic field The 5e Beholder creates an anti magic field that suppresses all magic within a 58 degree cone. The players cannot necessarily see the effect, but the DM needs a way to quickly show the cone's area during play. Solution: Dynamic Lighting and Field of Vision Even if you are not using DL for its light and movement blocking, you can set up your map and beholder as follows: Map: Use Dynamic Lighting with global illumination. Beholder: Has Sight, emits light (other players cannot see) in a 58 degree cone, bright light, 150 ft. For most of the time, (all of the time for the players) the field looks like this: Any time you need to see what is in the anti magic field, select the beholder and press Cmd/Ctrl-L, to see what it sees. You will see only the parts of the battlefield affected by the cone, but for the players, they still see the map normally. It's quick, simple and keeps the players guessing. Wizards of the Coast Beholder image used for demonstration purposes only. No copyright infringement intended.