The most USELESS monster.

Minotaurs will actually work well as a defensive unit. But who is going to go with them to level 4, and where will you get 100 Medusas? By the time you gather that many, the opponent will have 32 level 4 creatures + ranged attack protection, meaning Mirage, and petrification doesn't work on the undead, and Minotaurs seem to have a growth rate of 1 more, and petrification doesn't always work either.

Added 1 minute ago
Few people make it to 4 months. What kind of map should it be then?

Added 59 seconds ago
Although, if you have two castles, you can gather them in 2 months, but the opponent will still have more artifacts and experience because Medusas are slow, so you'll travel less, fight less, and get fewer artifacts.