To Blood Magic, Or Not To Blood Magic

[Goblin]

I have been playing a couple of games to familiarise my self with the costs and benefits of Blood Magic as the core strategic spell path. My question to those who have experience at both using Blood Magic and having it used on them is: What are it’s strengths and weaknesses?

Some that jump to mind (please feel free to expand on or tear these apart) are:

Strengths:
1. Accessibility of Slaves over Gems: Unlike Gems where you can luck out in finding sufficient of a particular type on which your strategy relies on, Blood slaves can be found easily in any province with population of greater than 8k.
2. Duel Purpose School: The Blood Magic research path has spells that are useful in both battle and as ritual casting – though the ritual ones are why I would follow it.
3. Versatility of troops available through Blood: You have fast flying troops, solid front line troops and host of top quality commanders and spell casters available to be summoned.
4. Maintenance Costs: Nearly all the troops summoned have no maintenance cost.

Weaknesses:
1. Opportunity cost of income: When drawing Blood slaves from a province you effectively write off any income that you would other wise receive. In order to keep unrest low you need to drop tax to zero (or have unrest rise to the point that you generate no income from the province any way).
2. Opportunity cost or research: While your mages are happily rounding up slaves for the slaughter in the fields, they are not in the labs developing new spells.
3. Cost of maintaining & defending Blood Slave factories: The maintenance cost of the mages, any defences needed to keep them safe and infrastructure (lab and possibly castle) in each province you farm for Blood Slaves.

I would especially like to hear from players that have used the school to devastating effect – or had it used to devastate them. Any suggestions on its best use or ways to counter it are also sought.

Regards,
Goblin.