The Market provides three economic functions: a Black Market, Auctions, and resource tax collection. Higher Market level makes Black Market products more luxurious and increases both the number of free tax collections and the amount per tax. Buildable at Keep 6; prerequisite for the Embassy (raise Market first). All menus stay available during upgrade. Tax collects resources a set number of times free, after which it costs Gems; the free count resets in 1 day -- a clean daily-collect action for a bot. The Auction House appears only during event periods. The Black Market unlocks at Market Lv11; the Duty Officer at Lv24 (increases Resource Tax Amount; ideal Yolande of Aragon or Michael VIII, which also buff Ground/Mounted troops). Keep-gated 1:1 (Keep n per Market n); cost Food/Lumber (to Lv6), Stone at Lv7, Ore at Lv12; construction-speed example to +610% by Lv50. For an economy bot: collect free tax daily (never pay gems for extra tax), treat the Black Market as the source for VIP items, production speedups and resource boxes, and value the Lv24 tax-yield duty officer. Detailed Black Market and Auction product/price lists live in separate guides.
Original research source: Evony Guide Wiki