The ages of Dominion.

[TigerBlood]

Magic is more prevelant in earlier ages. Not neccesarily in terms of spells and rituals, but gems tend to be more prevelant as magic sites tend to be more prevelant. Capitals also produce more gems in earlier era's.

Earlier era's tend to have more diverse indies. Not something you can plan for in pretender design/pre game strat, but some independants can definately influence your game.