Server merges happen irregularly at Evony's discretion (roughly once or twice a year historically), based on server environment, active player count, and availability of a matching server; notification email goes out ~10 days before merge, maintenance details the day before, merge completes within a few hours of maintenance. Effects for bot planning: personal data is preserved (building levels, VIP level, gems, gold, resources, sub cities, generals, troops, items); alliance remains but alliance buildings are removed (rebuild is free if already built pre-merge); players are randomly teleported onto the new shared map; all resource tiles and monsters reset and relics are removed; field troops auto-return to city; SvS/Battlefield rankings, Kings/Titles, and Monarch Competition all reset (last-stage rewards still sent; Throne War restarts after 24h); map bookmarks are deleted; duplicate names get numbered. A bot should re-scout resource tiles/relics and re-bookmark targets right after any merge.
Original research source: Evony Guide Wiki