Map Re-Creators Brush
Wondrous item, uncommon (requires attunement)
This looks like a small ornate wooden brush, with extremely fine bristles that seem as though the tip is wet with paint at all times. This brush never runs out of ink, and writes with ink of whatever color you want.
If you have a semi-accurate map of your immediate surrounding area, you can use this brush to draw on/update the map in a 30 foot radius centered on your location, and illusory versions of your changes/additions will appear for as long as the you stay within 30 feet of the illusion and are conscious.
The illusions are limited in that they are static visualizations, can only superimpose images, and can only have as much detail as you can add at scale on the map (making detailed illusions difficult to create well). The tactile characteristics of the area remains unchanged, so creatures entering an area covered in an illusion are likely to see through it. If the difference isn't obvious by touch, a creature carefully examining the Illusion can attempt an Intelligence (Investigation) check against your spell save DC to disbelieve it. A creature who saw the illusion suddenly pop into existence, or who is innately familiar with the area has advantage on this check. A creature who discerns the Illusion for what it is, sees it as a vague image superimposed on the terrain.
Attempting to update your map in this way during combat requires at least one action (potentially more if the DM determines the update is too complex to take place in 6 seconds).
Happy Customer Reviews
"Did you just flip the entire room around on that watch Goblin?"
"Yup"
"And now it's just staring at the other wall cause it thinks the door is there?"
"Yup"
"Goblins are stupid. Let's go."
Art Credit
Brushes, by Carthage