Most cost-efficient conjurable units?

[shatner]

The Summon Konoha Tengu spell which Yomi/Shinuyama/Jomon gets access to is very nice as of CBM 1.92. A single A1E1 caster spending 2 air gems gets you 5 sacred flying bird samurai (with katanas) who can throw lightning and fly during a storm. And the spell is only conjuration-3. That summon has been used to such good effect in our MA Jomon trial game that we're having to experiment with several balancing changes to the nation.