To open the doors at the end of the 1st level, two players located near the switch need to activate them at the same time (can be done with a mule).
On the second floor, the Living Statues appear as black dots on the map and are dormant until a player gets close, which activates them. Once all of them are killed, access is granted to the third level. Skeletons and battered skeletons will spawn when the statues start falling. Some of the statues are level 90, identified as "some ancient soldier" in their description. They have a chance to drop a Rose
When the last statue crumbles, THE SECRET ENTRANCE TO LEVEL THREE WILL OPEN in the South wall of Level 2. The door will remain open as long as there aren't any Living Statue in the level, which means that it will stay open until the room resets, since the Statues have no spawn rate.