Rainbow/1.03.25

Fey
Rainbows are amongst the very smallest of producable buildings in the game. They cost a lot of resources and aren't particularly tough, but their upgrades and unit access is amongst the best avaialble the Fey. Firstly, the Rainbow can produce Leprechauns, debatably one of the strongest Fey units in the game. These Leprechauns cost only Crystal, which can mean their production costs are nonexistant thanks to the Crystal Towers (and potentially the Fey hero, particularly a Merchant/Ice Mage). Leprechauns are extremely powerful ranged Magic damage units which fix any Gold resource problem the Fey had, by acting as a Level 1 Gold Mine. In addition to getting access to Leprechauns, the Rainbow also allows the most powerful Income researches in the game, all of which is potentially available at any stage of the game.