[Gregstrom]

I think it'd need to be something like Blood 4-5 to be a serious discouragement. B2 is fairly common for Blood nations, and forging 2 boosters isn't a serious cost. At B4, the cost would be 41 gems for the first 13 bone fiends (2x boosters, hammer), and then 3 for every 13 thereafter.

How about getting something like 8 fiends for 3 gems?

Maybe drop the MR on the bone fiends, to weaken them against banish?