Than it will come "visitors" to your maze.
If they rob your maze your horns will pause prododucing.
That's why you must increase the defense of the maze, with mobs.
The free upgrade it depends on your gearscore ad can be done outside of the maze, near at horrns, with talking to an NPC.
Once you will enter to the maze every room has a goblin, where you can increase additionally the defenders rank.
Rank 1 defense starts around 100.000 gold if I remmeber coreclty.
It will add a white-black buff to your mobs.
Rank 3 usually it is enough to wipe a full reincanations party. But rank 3 costs 300.000 gold or so.
Every time you will increase the rank the costs of a new rank will be increased. With 50% or even more?
Once I had the defense increased to lvl 11 or 13 or 14? But costs around 13 million gold! / room.
Usually just a few teams, with experience and rune and GS can clear it.
Does it worth?
No
You will never recover those money and in every 6-8 month is comming a nice patch wich will take the money invested in.