I'm afraid I'm no expert on multiplayer games, as the only multiplayer games of Civ IV I've ever tried were hotsteat games against myself. First, did you make sure that all the players were running the same version of my modmod? There would obviously be issues if you are not using identical versions. Second, could you share your .log files from the multiplayer game with OOS errors? I might be able to track down an issue from looking at those. You may need to first edit CivilizationIV.ini (found in the Documents\My Games\Beyond the Sword directory) so that LoggingEnabled = 1 and SynchLog = 1. It is probably best for RandLog = 1 and MessageLog = 1 too. I'm not sure, but you may need for all the players to modify their CivilizationIV.ini thus. It is the Necronomicon that is giving your units Mutation. Asylums Have a 10% chance of giving living, non-world units Crazed when they are first created. In vanilla FfH2, these same units are also given Enraged. In my version, it removes Enraged instead, but I'm thinking that might not actually do anything as there is no buildable unit that starts with Enraged from its xml defines. Crazed units still gain the Enraged promotion at random. Asylums will remove this promotion, but only if the unit is in the city at the start of the turn. (The <bApplyFreePromotionOnMove> tag is a misnomer, as in the BtS versions of FfH2 it actually only removes promotions at the start of a turn rather than on move.) The problem is that Enraged units tend not to stay in one place long enough to be in the Asylum to have their Enraged promotions removed. The other problem is that the check to remove promotions based on the buildings in the city probably happens before the check to randomly apply promotions based on other promotions.