Dark Ages is the 7th world in Plants vs. Zombies 2. It is the first world in Plants vs. Zombies 2 to be in a nighttime setting, similar to Night from Plants vs. Zombies. The mushrooms make their debut here. Sun does not fall from the sky in Dark Ages as it is set during the night. As it namesake says, Dark Ages takes place during the tenth century where culture and economy slowly deteriorate mankind that follows the decline of the Roman Empire. Also, the use of black magic like necromancy became the center of usage for evil purposes. Like in Ancient Egypt, tombstones appear in Dark Ages. However, they can now occasionally spawn by themselves and summon zombies through an ambush called "Necromancy!". Certain tombstones marked with a sun or Plant Food icon reward players with 100 sun and one Plant Food when destroyed respectively. If a grave spawns where there is a plant, that plant and all plants in front or behind it will move forward one column. All sun producing plants still do produce sun in these levels, but it is still recommended to use Sun-shrooms or Gold Blooms due to their lower costs.
The Plants that you can obtained in this world (My Take): Sun-shroom: Night 1 Puff-shroom: Night 2 Fume-shroom: Night 4 Scaredy-shroom: Night 6 Hypno-shroom: Night 11 Sun Bean: Night 15 Pea-nut: Night 19 Magnet-shroom: Night 23 Plantern: 15 Seed Packets Coffee Bean: 15 Seed Packets Oak Archer: 15 Seed Packets Cryo-shroom: 25 Seed Packets Pyro-shroom: 25 Seed Packets Ice-shroom: 20 Seed Packets Doom-shroom: 20 Seed Packets Gloom-shroom: 30 Seed Packets