The vibrating square is the square where the invocation ritual is to be performed for entry into Moloch's Sanctum. It is always located on the penultimate dungeon level of Gehennom, which could be between levels 44 and 52. It is the lowest level that can be reached without performing the ritual; until the ritual is performed, there is no staircase leading down from that level. Only the Sanctum level has a higher dungeon level number. The level with the vibrating square is in most other respects an ordinary maze level of Gehennom.