This is the old Pandemonium version before Dec 9th Patch.
Every 8 hours, monsters will raid your garden and you will have an option to defend against them.
Should you win, you will be awarded with Killing Stones.
Should you lose, seeds in your Special Field will be ravaged by monsters, and you will be unable to use your Special Field for 6(?) hours.
Pandemonium Size: Rank 1 [S] → Rank 2 [S] → Rank 3 [M-6] → Rank 4 [M-8] → Rank 5 [M-10]