[Endoperez]

I think the easyness comes from Sages. 1 in 8 sages have Blood, and with even a few of them your blood income can easily be twice that of any other path. And as you can generate more blood slaves using up population (=money), you can get absurd blood income. And the 80 slaves/contract gives you one Devil each turn. Each of those critters cost 7 slaves to summon, and would need a BBFF mage to boost. Using a Dwarven Hammer to make a Contract out of Blood Slaves may sound stupid, but it lowers the cost to 60. As you can see, Contracts cost the same price 8 Devils would.

Blood is easy to get, not with powerful mages, but with many.

In addition, after one high-level Blood mage, you can boost the level by Blood Athame, Brazen Skull and Armor of Souls, and possibly Earth Stone. I'd estimate that with 10 crimson Sages, empowering an Earth mage to Blood 3 and forging 4 boosters (or few Soul Contracts) can be done in 10 turns.