Tavern level 10 or below never yields historic generals (only Common/Uncommon). Historic-general (Legendary/Epic) odds rise with tavern level; per-6-slot-refresh chance (official in-game values, confirmed close to real test data): at Lv30, ~7.32% for a Legendary historic and ~2.51% for an Epic historic; at Lv37 (max tested), ~9.76%/3.38%. Real mass-refresh test at Lv30 (3,400 refreshes/170,000 gems) measured ~2.2-2.5% gold-historic rate per refresh, matching in-game figures within margin of error, though probability appeared to dip slightly the more refreshes were done in one sitting and certain generals clustered in bursts. Guidance: raise Tavern to at least Lv24+ before spending gems seriously chasing historic generals; even free/no-cost natural refreshes (checking tavern periodically) can yield a historic general (several users report free pulls at Lv10-20); cap serious gem-refresh sessions at ~100/day and try a different day if unlucky rather than over-spending in one sitting.
Original research source: Evony Guide Wiki
