There are 4 types of chest in the game. Mithril Chests cost 150 Linari, Gold Chests cost 480 Linari, Adamantine Chests cost 1280 Linari, Orichalcum Chests cost 3280 Linari. When you open a higher level chest, you have a better chance of getting valuable items, such as Gold-level Units or Relic-tier (orange) Equipment