Playing as the Sidar, it is possible to get instant shades. If you are playing a charismatic leader, it only takes 20 xp to get to level 6 and shade status. Instant shades might not sound like that big a deal, but now that each city can produce multiple units each turn, this gives you have unlimited production, unlimited money, unlimited science, and unlimited culture. Adopting the following civics give each of your starting units 2xp: Apprenticeship, Conquest, and Theocracy (plus have the state religion in your city). The Form of the Titan wonder gives 2 more xp. Settling a great commander gives you 2 more xp. A great commander is given to the first player to discover Military Strategy. Finally, if you build the Ride of the Nine Kings wonder, your calvary units all start with +10xp. All of which give you a total of 20xp in one city for each mounted unit created. An alternate way to get there without the Ride of the Nine Kings is to build the Altar of Luonnotar up to level 5 (divine) which gives your disciples +10xp. Disciples cost 60H. Each great engineer shade you settle provides 4 hammers and 3 science. Each horseman only costs 60 hammers. So 15 great engineers equal 1 new shade, not too abusive, right? But you also need to figure in production bonuses. Heroic Epic wonder, +100%, great commander +20%, Guild of Hammers, +1 hammer for each great engineer, Apprenticeship -10%. So each GE provides 5H X 2.1 = 10.5 hammers. So it only takes 6 GE to get another GE. This rapidly snowballs out of control. I have built Sidar super cities with 80+ GE and 50+ GM off of combat. Once you build Ride of the Nine Kings, you don't have to worry about combat anymore, you just win. You can pick cultural victory and plant unlimited GA in 3 cities. You can get unlimited cash off of GM, unlimited research off of GS, and unlimited production off of GE. The set of circumstances required to set up unlimited shades is pretty late game, so I don't know that a fix is needed. This might still be considered an exploit though.