All nodes have been built, so you can change all -non tower of divination ones to enchantment.
Then just focus on getting as much gold as possible, through building markets, wealth, spreading kilmorph, deleting units etc.
Remember to trade away the free death mana from the tower of necromancy, and dispel the other "evil" nodes.
Also rejoin the overcouncil, and switch religions to kilmorph to build a host of soldiers of kilmorph to rush it.
At about 20-25 thousand gold (depending on rush cost and soldiers of kilmorph) rush buy the tower of divination, take strength of will, and rush the tower of mastery.