Hell
Hell is unlocked by collecting 10 (or more) treasures in 9 lands. The monsters are Lesser Demons, which move at half speed but otherwise move like the player, and Greater Demons, which also move at half speed but cannot be killed. Greater Demons turn into Lesser Demons if you kill 10 Lesser Demons after the Greater Demon spawns.
After collecting at least 10 Demon Daisies, Orbs of Yendor start to appear. Successfully picking up an Orb of Yendor qualifies as winning the game, and will cause the game over screen to display a Congratulations message when the player dies afterwards. However, the Orb cannot be picked up directly: touching the Orb will reveal the location of the Key required to unlock the Orb. The player must obtain this Key before the Orb can be picked up.