[General Tacticus]

As Norfleet said, each blood slave sacrificed gives you the equivalent of a temple check in the province where it is sacrificed. Multiple sacrifices, even by the same priest, give multiple checks. A sacrifice can only happen in a temple, and only one priest can perform sacrifices (but he can perform more than one, with high blood and/or a jade knife) in each temple.

In other words, put a Mictlan priest in a temple, with order to sacrifice one blood slave a turn, and you have a regular temple. Tell him to kill 2 slaves a turn (assuming he can) and you have the equivalent of 2 temples in the province...

Also, it seems (I'll have to check properly some time) that if you choose a generic pretender, he does increase dominion by himself, but if you choose one of the Mictlan-specific ones, he doesn't. The prophet does not spread dominion. Restless worshippers, IIRC, only diminish enemy dominion, but do not increase your own. Victory point seem to spread dominion (I'll have to make a "scientific" test sometime, not just rely on what I recall of my Mictlan games...)

By not putting any temple in or near a province, or by not doing sacrifices in those temple, you can pretty much assure that your dominion won't grow in that province - quite easy for Mictlan.